UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-K

(Mark One):

x Annual report pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934.

For the fiscal year ended December 31, 20132014

¨ Transition report pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934.

For the transition period from              to             

Commission File Number: 001-14195

American Tower Corporation

(Exact name of registrant as specified in its charter)

116 Huntington Avenue

Boston, Massachusetts 02116

(Address of principal executive offices)

Telephone Number (617) 375-7500

(Registrant’s telephone number, including area code)

Securities registered pursuant to Section 12(b) of the Act:

Securities registered pursuant to Section 12(g) of the Act:

None

Indicate by check mark if the registrant is a well known seasoned issuer, as defined in Rule 405 of the Securities Act:    Yes  x    No  ¨

Indicate by check mark if the registrant is not required to file reports pursuant to Section 13 or Section 15(d) of the Act:    Yes  ¨    No  x

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days:    Yes  x    No  ¨

Indicate by check mark whether the registrant has submitted electronically and posted on its corporate Web site, if any, every Interactive Data File required to be submitted and posted pursuant to Rule 405 of Regulation S-T during the preceding 12 months (or for such shorter period that the registrant was required to submit and post such files).    Yes  x    No  ¨

Indicate by check mark if disclosure of delinquent filers pursuant to Item 405 of Regulation S-K is not contained herein, and will not be contained, to the best of registrant’s knowledge, in definitive proxy or information statements incorporated by reference in Part III of the Form 10-K or any amendment to this Form 10-K.  x

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, or a smaller reporting company. See definition of “large accelerated filer,” “accelerated filer” and “smaller reporting company” in Rule 12b-2 of the Exchange Act. (Check One):

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act):    Yes  ¨    No  x

The aggregate market value of the voting and non-voting common stock held by non-affiliates of the registrant as of June 30, 20132014 was approximately $28.7$35.3 billion, based on the closing price of the registrant’s common stock as reported on the New York Stock Exchange as of the last business day of the registrant’s most recently completed second quarter.

As of February 14, 2014,13, 2015, there were 395,017,519396,708,636 shares of common stock outstanding.

DOCUMENTS INCORPORATED BY REFERENCE

Portions of the definitive proxy statement (the “Definitive Proxy Statement”) to be filed with the Securities and Exchange Commission relative to the Company’s 20142015 Annual Meeting of Stockholders are incorporated by reference into Part III of this Report.

AMERICAN TOWER CORPORATION

TABLE OF CONTENTS

FORM 10-K ANNUAL REPORT

FISCAL YEAR ENDED DECEMBER 31, 20132014

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AMERICAN TOWER CORPORATION

TABLE OF CONTENTS—(Continued)

FORM 10-K ANNUAL REPORT

FISCAL YEAR ENDED DECEMBER 31, 20132014

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS

This Annual Report contains statements about future events and expectations, or forward-looking statements, all of which are inherently uncertain. We have based those forward-looking statements on our current expectations and projections about future results. When we use words such as “anticipates,” “intends,” “plans,” “believes,” “estimates,” “expects” or similar expressions, we do so to identify forward-looking statements. Examples of forward-looking statements include, but are not limited to, statements we make regarding the Proposed Verizon Transaction (as defined in this Annual Report), future prospects of growth in the communications site leasing industry, the effects of consolidation among companies in our industry and among our tenants and other competitive pressures, the level of future expenditures by companies in this industry and other trends in this industry, changes in zoning, tax and other laws and regulations, economic, political and other events, particularly those relating to our international operations, our substantial leverage and debt service obligations, our future financing transactions, our plans to fund our future liquidity needs, the level of future expenditures by companies in this industry and other trends in this industry, our ability to maintain or increase our market share, our future operating results, our ability to remain qualified for taxation as a real estate investment trust (“REIT”), the amount and timing of any future distributions including those we are required to make as a REIT, our future capital expenditure levels, our ability to protect our rights to the land under our towers and natural disasters and similar events and our future purchases under our stock repurchase program.events. These statements are based on our management’s beliefs and assumptions, which in turn are based on currently available information. These assumptions could prove inaccurate. These forward-looking statements may be found under the captions “Business” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” as well as in this Annual Report generally.

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You should keep in mind that any forward-looking statement we make in this Annual Report or elsewhere speaks only as of the date on which we make it. New risks and uncertainties arise from time to time, and it is impossible for us to predict these events or how they may affect us. In any event, these and other important factors, including those set forth in Item 1A of this Annual Report under the caption “Risk Factors,” may cause actual results to differ materially from those indicated by our forward-looking statements. We have no duty and do not intend to update or revise the forward-looking statements we make in this Annual Report, except as may be required by law. In light of these risks and uncertainties, you should keep in mind that the future events or circumstances described in any forward-looking statement we make in this Annual Report or elsewhere might not occur. References in this Annual Report to “we,” “our” and the “Company” refer to American Tower Corporation and its predecessor, as applicable, individually and collectively with its subsidiaries as the context requires.

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PART I

Overview

We are a leadingglobal independent owner, operator and developer of wireless and broadcast communications real estate. Our primary business is the leasing antennaof space on multi-tenant communications sites to wireless service providers, radio and television broadcast companies, wireless data and data providers, government agencies and municipalities and tenants in a number of other industries. We refer to this business as our rental and management operations, which accounted for approximately 98% of our total revenues for the year ended December 31, 2013.2014. Through our network development services business, we offer tower-related services domestically, including site acquisition, zoning and permitting services and structural analysis services, which primarily support our site leasing business and the addition of new tenants and equipment on our sites. Since January 1, 2012, we have been organized and have qualified as a REIT for federal income tax purposes.business.

Our communications real estate portfolio of 67,41875,594 communications sites, as of December 31, 2013,2014, includes wireless and broadcast28,566 communications towers domestically, 46,598 communications towers internationally and 430 distributed antenna system (“DAS”) networks, which provide seamless coverage solutions in certain in-building and outdoor wireless environments. Our portfolio primarily consists of towers that we own and towers that we operate pursuant to long-term lease arrangements, including, as of December 31, 2013, 27,739 towers domestically and 39,330 towers internationally. Our portfolio also includes 349 DAS networks.arrangements. In addition to the communications sites in our portfolio, we manage rooftop and tower sites for property owners under various contractual arrangements andarrangements. We also hold property interests that we lease to communications service providers and third-party tower operators.

American Tower Corporation was originally created as a subsidiary of American Radio Systems Corporation in 1995 and was spun off into a free-standing public company in 1998. Since inception, we have grown our communications real estate portfolio through acquisitions, long-term lease arrangements and site development. In October 2013, we significantly expanded our portfolio through our acquisition of MIP Tower Holdings LLC (“MIPT”), a private REIT and parent company to Global Tower Partners (“GTP”), an owner and operator of approximately 5,370 communications sites, through its various operating subsidiaries, in the United States, Costa Rica and Panama. GTP also manages rooftops and holds property interests that it leases to communications service providers and third-party tower operators. We believe the acquisition provides us with key strategic and financial advantages, due to the high quality of the assets, which are in locations complementary to our portfolio. For more information on our acquisition of MIPT, see note 6 to our consolidated financial statements included in this Annual Report.

We are a holding company and conduct our operations through our directly and indirectly owned subsidiaries and joint ventures. Our principal domestic operating subsidiaries are American Towers LLC and SpectraSite Communications, LLC. We conduct our international operations primarily through our subsidiary, American Tower International, Inc., which in turn conducts operations through its various international holding and operating subsidiaries and joint ventures. Our

On February 5, 2015, we signed a definitive agreement with Verizon Communications, Inc. (“Verizon”) pursuant to which we expect to acquire the exclusive right to lease, acquire or otherwise operate and manage up to 11,489 wireless communications sites for $5.056 billion in cash at closing (the “Proposed Verizon Transaction”), subject to certain conditions and limited adjustments.

We operate as a REIT and therefore are generally not subject to U.S. federal income taxes on our income and gains that we distribute to our stockholders, including the income derived from leasing space on our towers. However, even as a REIT, we remain obligated to pay income taxes on earnings from our taxable REIT subsidiaries (“TRSs”). In addition, our international assets and operations, consistincluding those designated as direct or indirect qualified REIT subsidiaries or other disregarded entities of a REIT (collectively, “QRSs”), continue to be subject to taxation in the foreign jurisdictions where those assets are held or those operations are conducted.

The use of TRSs enables us to continue to engage in certain businesses while complying with REIT qualification requirements. We may, from time to time, change the election of previously designated TRSs to be treated as QRSs, and may reorganize and transfer certain assets or operations from our TRSs to other subsidiaries, including QRSs. During the year ended December 31, 2014, we restructured certain of our German subsidiaries and certain of our domestic TRSs, which included a portion of our network development services segment and indoor DAS networks business, to be treated as QRSs. As a result, as of December 31, 2014, our QRSs include our domestic tower leasing business, most of our operations in Brazil, Chile, Colombia, Costa Rica, Germany Ghana, India,and Mexico Panama, Peru, South Africa and Uganda.a portion of our network development services segment and indoor DAS networks business.

Our continuing operations are reported in three segments: (i) domestic rental and management, (ii) international rental and management and (iii) network development services. For more information about our

business segments, as well as financial information about the geographic areas in which we operate, see Item 7 of this Annual Report under the caption “Management’s Discussion and Analysis of Financial Condition and Results of Operations” and note 21 to our consolidated financial statements included in this Annual Report.

We hold and operate certain of our assets through one or more taxable REIT subsidiaries (“TRSs”). The non-REIT qualified businesses that we hold through TRSs include most of our network development services segment. In addition, we have included most of our international operations and managed networks business within our TRSs.

We may, from time to time, change the election of previously designated TRSs to be treated as qualified REIT subsidiaries or other disregarded entities (“QRSs”), and may reorganize and transfer certain assets or operations from our TRSs to other subsidiaries, including QRSs. We changed the previous TRS election for certain of our Mexican subsidiaries to be treated as QRSs as of March 1, 2013. In addition, we restructured certain of our domestic TRSs to be treated as QRSs as of January 1, 2014.

Products and Services

Rental and Management Operations

Our rental and management operations accounted for approximately 98%, 97%98% and 98%97% of our total revenues for the years ended December 31, 2014, 2013 and 2012, and 2011, respectively. Our revenue is primarily generated from tenant leases. Our tenants lease space on our communications site real estate, where they install and maintain their individual communications network equipment. Our revenue is primarily generated from tenant leases. The annual rentalRental payments vary considerably depending upon numerous factors, including, but not limited to, tower location, amount and type of tenant equipment on the tower, ground space required by the tenant and remaining tower capacity. Our tenant leases are typically non-cancellable and have annual rent escalations. Our primary costs typically include ground rent (which is primarily fixed, with annual cost escalations), and power and fuel costs, some of which may be passed through to our tenants, as well as property taxes and repairs and maintenance. Our rental and management operations have generated consistent incremental growth in revenue and have low cash flow volatility due to the following characteristics:

Our domestic rental and management segment is comprised of our nationwide networkoperations include the operation of communications sites that enable us to addresstowers, managed networks, the needsleasing of national, regional, local and emerging communications service providers in the United States, as well as customers in a number of other industries. Our domestic rental and management segment also includes property interests that we lease to communications service providers and third-party tower operators.the provision of backup power through shared generators. Our domestic rental and management segment accounted for approximately 65%, 67%65% and 72%67% of our total revenues for the years ended December 31, 2014, 2013 and 2012, and 2011, respectively.

Our international rental and management segment, which is comprisedconsists of communications sites in Brazil, Chile, Colombia, Costa Rica, Germany, Ghana, India, Mexico, Panama, Peru, South Africa and Uganda, provides a source of growth and diversification, including exposure to markets in various stages of wireless network development. In November 2014, we expanded our global footprint by signing an agreement to acquire over 4,800 communications sites in Nigeria. Our international rental and management segment accounted for approximately 33%, 30%33% and 26%30% of our total revenues for the years ended December 31, 2014, 2013 and 2012, and 2011, respectively.

Our rental and management operations include the operation of wireless and broadcast communications towers and managed networks, rooftop management, the leasing of property interests and the provision of backup power through shared generators domestically.

Communications Towers. Approximately 96%95%, 96% and 98%96% of revenue in our rental and management segments was attributable to our communications towers for the years ended December 31, 2014, 2013 2012 and 2011,2012, respectively.

We lease real estate on our communications towers to tenants providing a diverse range of communications services, including personal communications services, cellular voice and data, broadcasting, enhanced specialized mobile radio, mobile video and fixed microwave. Our top domestic and international tenants by revenue are as follows:

Accordingly, we are subject to certain risks, as set forth in Item 1A of this Annual Report under the caption “Risk Factors—A substantial portion of our revenue is derived from a small number of tenants, and we are sensitive to changes in the creditworthiness and financial strength of our tenants.” In addition, we are subject to risks related to our international operations, as set forth under the caption “Risk Factors—Our foreign operations are subject to economic, political and other risks that could materially and adversely affect our revenues or financial position, including risks associated with fluctuations in foreign currency exchange rates.”

Managed Networks, Property Interests and Shared Generators.In addition to our communications sites, we also own and operate several types of managed network solutions, provide communications site management services to third parties, manage and/orand lease property interests under carrier or other third-party communications sites and provide back-up power sources to tenants at our sites.

other barriers may prevent or delay deployment of more traditional wireless communications sites. We are also currently evaluating other complementary network strategies, such as small cell deployments. In addition, we provide management services to property owners in the United States and certain international markets who own rooftops capable of hosting wireless communications equipment. We obtain rights to manage a rooftop by entering into a contract with a property owner pursuant to which we receive a percentage of occupancy or license fees paid to that property owner by the wireless carriers and other tenants. As the demand for advanced wireless devices in urban markets evolves, we continue to evaluate infrastructure that may support our tenants’ networks in these areas.

Network Development Services

Through our network development services, segment, we offer tower-related services domestically, including site acquisition, zoning and permitting services and structural analysis services. Network development services which primarily support our site leasing business and the addition of new tenants and equipment on our sites.sites, including in connection with provider network upgrades. This segment accounted for approximately 2%, 3%2% and 2%3% of our total revenues for the years ended December 31, 2014, 2013 2012 and 2011,2012, respectively.

Site Acquisition, Zoning and Permitting. We engage in site acquisition services on our own behalf in connection with our tower development projects, as well as on behalf of our tenants. We typically work with our tenants’ engineers to determine the geographic areas where new towercommunications sites will best address the tenants’ needs and meet their coverage objectives. Once a new site is identified, we acquire the rights to the land or structure on which the site will be constructed, and we manage the permitting process to ensure all necessary approvals are obtained to construct and operate the communications site.

Structural Analysis. We offer structural analysis services to wireless carriers in connection with the installation of their communications equipment on our towers. Our team of engineers can evaluate whether a tower structure can support the additional burden of the new equipment or if an upgrade is needed, which enables our tenants to better assess potential sites before making an installation decision. Our structural analysis capabilities enable us to provide higher quality service to our existing tenants by, among other things, reducing the time required to achieve operational readiness, while also providing opportunities to offer structural analysis services to third parties.

Strategy

Operational Strategy

Our operational strategy is to capitalize on the global growth in the use of wireless communications services and the evolution of advanced wireless handsets, tablets and other mobile devices, and the corresponding expansion of communications infrastructure required to deploy current and future generations of wireless communications technologies. To achieve this, our primary focus is to (i) increase the leasing of our existing communications real estate portfolio, (ii) invest in and selectively grow our communications real estate portfolio, (iii) further improve upon our operational performance and (iv) maintain a strong balance sheet. We believe these efforts will further support and enhance our ability to capitalize on the growth in demand for wireless infrastructure.

resulted in significant capital spending by major wireless carriers. As a result, we anticipate consistent demand for our communications sites because they are attractively located for wireless service providers and have capacity available for additional tenants. In the United States, incremental carrier capital spending is being driven primarily by the build-out of fourth generation (4G) networks, while our international markets are in various stages of network development. As of December 31, 2013, we had a global average of approximately 1.9 tenants per tower. We believe that many of our towers have capacity for additional tenants and that substantially all of our towers that are currently at or near full structural capacity can be upgraded or augmented to meet future tenant demand with relatively modest capital investment. Therefore, we will continue to target our sales and marketing activities to increase the utilization and return on investment of our existing communications sites.

Capital Allocation Strategy

The objective of our capital allocation strategy is to simultaneously increase adjusted funds from operations and our return on invested capital. To maintain our qualification for taxation as a REIT, status we are required to distribute to our stockholders annually an amount equal to at least 90% of our REIT taxable income (determined before the deduction for distributed earnings and excluding any net capital gain). After complying with our REIT distribution requirements and paying dividends on our preferred stock, we plan to continue to allocate our available capital among investment alternatives that meet our return on investment criteria, while taking into account the repayment of debt, as necessary, to reduce our net leverage to be within our long-term target range. Accordingly, we expect to continue to deploy our capital through our annual capital expenditure program, including land purchases and new site construction and acquisitions. In addition, we intend to return our remaining excess capital, if any, to stockholders through our stock repurchase program or by declaring special distributions from time to time. During 2013, we generated $1.6 billion of cash from operating activities, which along with incremental debt, was used to fund nearly $5.2 billion of investments, including $4.5 billion of acquisitions and $724.5 million of

capital expenditures. In addition, in 2013, we repurchased $145.0 million, including commissions and fees, of our common stock and paid regular cash distributions in the aggregate of approximately $434.7 million to our stockholders.

During 2014, we generated $2.1 billion of cash from operating activities, which along with incremental debt, was used to fund $1.9 billion of investments, including $1.0 billion of acquisitions and $974.4 million of capital expenditures. In addition, in 2014, we paid regular cash distributions in the aggregate of approximately $404.6 million to our common stockholders and approximately $16.0 million to our preferred stockholders.

International Growth Strategy

We believe that, in certain international markets, we can create substantial value by either establishing a new, or expanding our existing independent wirelesscommunications real estate leasing business. Therefore, we expect we will continue to seek international growth opportunities where we believe our risk adjustedrisk-adjusted return objectives can be

achieved. We strive to maintain a diversified approach to our international growth strategy by complementing our presence in emerging markets with operations in more developed and established markets, which enables us to leverage multiple stages of wireless network development throughout our global footprint. Our international growth strategy includes a disciplined, individualized market evaluation, in which we conduct the following analyses:

Recent Transactions

Acquisitions

From January 1, 20132014 through December 31, 2013,2014, we increased our communications site portfolio by approximately 13,0708,450 sites, including approximately 2,3703,133 build-to-suits, and we believe the assets constructed and acquired will be accretive to our consolidated operating margins. AcquisitionsSignificant acquisitions during the year ended December 31, 2013 included:

(November 2013) and approximately 1,940 communications sites in Brazil from NII (December 2013). These acquisitions strengthened our presence in our legacy markets by expanding our site portfolio by nearly 30% in Latin America.

We continue to evaluate potential complementary services to supplement our tower site growth and expansion strategy, as well as opportunities to acquire larger communications real estate portfolios that we believe we can effectively integrate into our existing business. For more information about our acquisitions, see note 6 to our consolidated financial statements included in this Annual Report.

Financing Transactions

During the year ended December 31, 2013,2014, to complement our operational strategy to selectively invest in and grow our communications real estate portfolio, we raised capital, thereby increasingstrengthened our financial flexibility and our ability to return value to our stockholders. Significantbalance sheet by completing a number of

key financing transactions in 2013 includedinitiatives, including those set forth below. For more information about our financing transactions, see Item 7 of this Annual Report under the caption “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Liquidity and Capital Resources” and note 8 to our consolidated financial statements included in this Annual Report.

Securitization. In March 2013, we completed a securitization transaction (the “Securitization”) involving assets related to 5,195 wireless and broadcast communications towers (the “Secured Towers”) owned by two of our special purpose subsidiaries, through a private offering of $1.8 billion of Secured Tower Revenue Securities, Series 2013-1A and Series 2013- 2A (collectively, the “Securities”). We used the net proceeds from the Securitization to refinance the $1.75 billion of Commercial Mortgage Pass-Through Certificates, Series 2007-1 issued in the securitization transaction completed in May 2007 (the “Certificates”).

Senior Notes Offerings.In January 2013,2014, we completed a registered public offering through a reopening of $1.0 billion aggregate principal amount of 3.50% senior unsecured notes due 2023 (the “3.50% Notes”). In August 2013, we completed a registered public offering of $750 million aggregate principal amount ofour (i) 3.40% senior unsecured notes due 2019 (the “3.40% Notes”) and $500 million, in an aggregate principal amount of $250.0 million and our (ii) 5.00% senior unsecured notes due 2024 (the “5.00% Notes”)., in an aggregate principal amount of $500.0 million. In August 2014, we completed a registered public offering of our 3.450% senior unsecured notes due 2021 (the “3.450% Notes”) in an aggregate principal amount of $650.0 million. We used the net proceeds from each of these notes offeringsoffering primarily to repay certain indebtedness under our existing credit facilities.

Credit Facilities.Mandatory Convertible Preferred Stock Offering.In May 2014, we completed a registered public offering of 6,000,000 shares of our 5.25% Mandatory Convertible Preferred Stock, Series A, par value $0.01 per share (the “Mandatory Convertible Preferred Stock”). We increasedused the net proceeds from the offering to fund acquisitions initially funded by indebtedness incurred under our borrowing capacity and financial flexibility by entering into a$2.0 billion multi-currency $1.5 billion senior unsecured revolving credit facility in June 2013, which was subsequently increased to $2.0 billion (the “2013 Credit Facility”).

Credit Facilities.In September 2014, we entered into an amendment and a 364-dayrestatement of our $1.0 billion senior unsecured revolving credit facility in September 2013 (the “Short-Term“2012 Credit Facility”, as amended and restated, the “2014 Credit Facility”)., which, among other things, increased the commitments thereunder to $1.5 billion and extended the maturity date to January 31, 2020. As a result, as of December 31, 2013,2014, we had the ability to borrow up to $2.0$2.4 billion under our existing credit facilities, net of any outstanding letters of credit. We also entered into a $1.5 billion unsecured term loan in October 2013 (the “2013 Term Loan”), and repaid our $750.0 million unsecured term loan entered into in June 2012 (the “2012 Term Loan”).

Regulatory Matters

Towers and Antennas. Our domestic and international tower business is subject to national, state and local regulatory requirements with respect to the registration, siting, construction, lighting, marking and maintenance of our towers. In the United States, which accounted for approximately 67%66% of our total rental and management

revenue for the year ended December 31, 2013,2014, the construction of new towers or modifications to existing towers may require pre-approval by the Federal Communications Commission (“FCC”) and the Federal Aviation Administration (“FAA”), depending on factors such as tower height and proximity to public airfields. Towers requiring pre-approval must be registered with the FCC and maintained in accordance with FAA standards. Similar requirements regarding pre-approval of the construction and modification of towers are imposed by regulators in other countries. Non-compliance with applicable tower-related requirements may lead to monetary penalties or site deconstruction orders.

Furthermore, in India, each of our subsidiaries holds an Infrastructure Provider Category-I license (“IP-I”) issued by the Indian Ministry of Communications and Information Technology, which permits us to provide tower space to companies licensed as telecommunications service providers under the Indian Telegraph Act of 1885. As a condition to the IP-I, the Indian government has the right to take over telecommunications infrastructure in the case of emergency or war. In Ghana, our subsidiary holds a Communications Infrastructure License, issued by the National Communications Authority (“NCA”), which permits us to establish and maintain passive telecommunications infrastructure services and DAS networks for communications service providers licensed by the NCA. While we are required to provide tower space on a non-discriminatory basis, we may negotiate mutually agreeable terms and conditions with such service providers. In Chile, our subsidiary is classified as a Telecom Intermediate Service Provider. We have received a number of site specific concessions and are working with the Chilean Subsecretaria de Telecommunicaciones to receive concessions on our remaining sites in Chile.

Our international business operations may be subject to increased licensing fees or ownership restrictions. For example, the Telecom Regulatory Authority of India has recommended to the Indian Department of Telecommunications changes in annual licensing fees for tower companies based on revenues generated, as well as the potential implementation of certain limitations on foreign ownership. To date, such changes have not been formally adopted. In South Africa, the Broad-Based Black Economic Empowerment Act, 2003 (the “BBBEE Act”)

has established a legislative framework for the promotion of economic empowerment of South African citizens disadvantaged by Apartheid, and accordingly,Apartheid. Accordingly, the BBBEE Act and related codes measure BBBEE Act compliance and good corporate practice by the inclusion of certain ownership, management control, employment equity and other metrics for companies that do business there. CertainIn addition, certain municipalities in Brazil and India have sought to impose permit fees based upon structural or operational requirements of towers. In addition, ourOur foreign operations may be affected if a country’s regulatory authority restricts or revokes spectrum licenses of certain wireless service providers.providers or implements limitations on foreign ownership.

In all countries where we operate, we are subject to zoning restrictions and restrictive covenants imposed by local authorities or community organizations. While these regulations vary, they typically require tower owners or tenants to obtain approval from local authorities or community standards organizations prior to tower construction or the addition of a new antenna to an existing tower. Local zoning authorities and community residents often oppose construction in their communities, which can delay or prevent new tower construction, new antenna installation or site upgrade projects, thereby limiting our ability to respond to tenant demand. In addition, zoning regulations can increase costs associated with new tower construction, tower modifications, and additions of new antennas to a site or site upgrades. For instance, in June 2012, the Chilean government passed legislation retroactively imposing certain zoning restrictions on telecommunications towers, in response to which we developed a remediation plan. Existing regulatory policies may adversely affect the associated timing or cost of such projects and additional regulations may be adopted that cause delays or result in additional costs to us. These factors could materially and adversely affect our construction activities and operations. In the United States, the Telecommunications Act of 1996 prohibits any action by state and local authorities that would discriminate between different providers of wireless services or ban altogether the construction, modification or placement of communications sites. It also prohibits state or local restrictions based on the environmental effects of radio frequency emissions to the extent the facilities comply with FCC regulations. Further, in February 2012, the United States government adopted regulations requiring that local and state governments approve modifications or collocations that qualify as eligible facilities under the regulations.

Portions of our business are subject to additional regulations, for example, in a number of states throughout the United States, certain of our subsidiaries hold Competitive Local Exchange Carrier (CLEC) or other status, in connection with the operation of our outdoor DAS networks business. In addition, we or our domestic and international tenants may be subject to new regulatory policies in certain jurisdictions from time to time that may materially and adversely affect our business or the demand for our communications sites.

Environmental Matters. Our domestic and international operations are subject to various national, state and local environmental laws and regulations, including those relating to the management, use, storage, disposal, emission and remediation of, and exposure to, hazardous and non-hazardous substances, materials and wastes and the siting of our towers. We may be required to obtain permits, pay additional property taxes, comply with regulatory requirements and make certain informational filings related to hazardous substances or devices used to provide power such as batteries, generators and fuel at our sites. Violations of these types of regulations could subject us to fines or criminal sanctions.

Additionally, in the United States and many other international markets where we do business, before constructing a new tower or adding an antenna to an existing site, we must review and evaluate the impact of the action to determine whether it may significantly affect the environment and whether we must disclose any significant impacts in an environmental assessment. If a tower or new antenna might have a material adverse impact on the environment, FCC or other governmental approval of the tower or antenna could be significantly delayed.

Health and Safety. In the United States and in other countries where we operate, we are subject to various national, state and local laws regarding employee health and safety, including protection from radio frequency exposure.

Competition

We compete, both for new business and for the acquisition of assets, with other public tower companies, such as Crown Castle International Corp., SBA Communications Corporation and GTL Infrastructure Limited, wireless carrier tower consortiumsconsortia such as Indus Towers and private tower companies, independent wireless carriers, tower owners, broadcasters and owners of non-communications sites, including rooftops, utility towers, water towers and other alternative structures. We believe that site location and capacity, network density, price, quality and speed of service have been, and will continue to be, significant competitive factors affecting owners, operators and managers of communications sites.

Our network development services business competes with a variety of companies offering individual, or combinations of, competing services. The field of competitors includes site acquisition consultants, zoning consultants, real estate firms, right-of-way consultants, structural engineering firms, tower owners/managers, telecommunications equipment vendors who can provide turnkey site development services through multiple subcontractors and our tenants’ personnel. We believe that our tenants base their decisions for network development services on various criteria, including a company’s experience, local reputation, price and time for completion of a project.

Customer Demand

Our strategy is predicated on the belief that wireless service providers will continue to invest in the coverage, quality and capacity of their networks in both our domestic and international markets, driving demand for our communications sites.

As consumer demand for and use of advanced wireless services in the United States grow, wireless service providers may be compelled to deploy new technology and equipment, further increase the cell density of their existing networks and expand their network coverage.

We believe demand for our communications sites will continue as wireless service providers seek to increase the quality, coverage area and capacity of their existing networks, while also investing in next generation data networks. To meet these network objectives, we believe wireless carriers will continue to outsource their communications site infrastructure needs as a means to accelerate network development and more efficiently use their capital, rather than construct and operate their own communications sites and maintain their own communications site operation and development capabilities. In addition, because our network development services are complementary to our rental and management business, we believe demand for our network development services will continue, consistent with industry trends.

Our customer demand could be adversely affected by the emergence and growth of new technologies, which could make it possible for wireless carriers to increase the capacity and efficiency of their existing networks without the need for incremental cell sites. The increased use of spectrally efficient technologies or the availability of significant incremental spectrum in the marketplace could potentially relieve a portion of our tenants’ network capacity problems, and as a result, could reduce the demand for tower-based antenna space. Additionally, certain complementary network technologies, such as small cell deployments, could shift a portion of our tenants’ network investments away from the traditional tower-based networks, which may reduce the need for carriers to add more equipment at certain communications sites.

In addition, anyAny increase in the use of network sharing, roaming or resale arrangements by wireless service providers could adversely affect customer demand for tower space. These arrangements enable a provider to serve its customers outside the provider’s license area, to give licensed providers the right to enter into arrangements to serve overlapping license areas and to permit non-licensed providers to enter the wireless marketplace. Consolidation among wireless carriers could similarly impact customer demand for our communications sites because the existing networks of wireless carriers often overlap. In addition, wireless carriers sharing their sites or permitting equipment location swapping on their sites with other carriers to a significant degree could reduce demand for our communications sites. Further, our tenants may be subject to new regulatory policies from time to time that materially and adversely affect the demand for our communications sites.

In addition, our customer demand could be adversely affected by the emergence and growth of new technologies, which could make it possible for wireless carriers to increase the capacity and efficiency of their existing networks without the need for incremental cell sites. The increased use of spectrally efficient technologies or the availability of significant incremental spectrum in the marketplace could potentially relieve a portion of our tenants’ network capacity problems, and as a result, could reduce the demand for tower-based antenna space. Additionally, certain complementary network technologies, such as small cell deployments, could shift a portion of our tenants’ network investments away from the traditional tower-based networks, which may reduce the need for carriers to add more equipment at certain communications sites.

Employees

As of December 31, 2013,2014, we employed 2,7162,974 full-time individuals and consider our employee relations to be satisfactory.

Available Information

Our Internet website address iswww.americantower.com. Information contained on our website is not incorporated by reference into this Annual Report, and you should not consider information contained on our website as part of this Annual Report. You may access, free of charge, our Annual Reports on Form 10-K, Quarterly Reports on Form 10-Q and Current Reports on Form 8-K, plus amendments to such reports as filed or furnished pursuant to Sections 13(a) or 15(d) of the Securities Exchange Act of 1934, as amended (“Exchange Act”), through the “Investor Relations” portion of our website as soon as reasonably practicable after we electronically file such material with, or furnish it to, the Securities and Exchange Commission (“SEC”).

We have adopted a written Code of Ethics and Business Conduct Policy (the “Code of Conduct”) that applies to all of our employees and directors, including, but not limited to, our principal executive officer, principal financial officer and principal accounting officer or controller or persons performing similar functions. The Code of Conduct, our corporate governance guidelines and the charters of the audit, compensation and nominating and corporate governance committees of our Board of Directors are available at the “Investor Relations” portion of our website. In the event we amend the Code of Conduct, or provide any waivers under the Code of Conduct to our directors or executive officers, we will disclose these events on our website as required by the regulations of the New York Stock Exchange (the “NYSE”) and applicable law.

In addition, paper copies of these documents may be obtained free of charge by writing us at the following address: 116 Huntington Avenue, Boston, Massachusetts 02116, Attention: Investor Relations; or by calling us at (617) 375-7500.

Decrease in demand for our communications sites would materially and adversely affect our operating results, and we cannot control that demand.

Factors affecting the demand for our communications sites and, to a lesser extent, our network development services, could materially and adversely affect our operating results. Those factors include:

Any downturn in the economy or disruption in the financial and credit markets could impact consumer demand for wireless services. If wireless service subscribers significantly reduce their minutes of use, or fail to

widely adopt and use wireless data applications, our wireless service provider tenants could experience a decrease in demand for their services. As a result, our tenants may scale back their capital expenditure plans, which could materially and adversely affect leasing demand for our communications sites and our network development services business, which could have a material adverse effect on our business, results of operations or financial condition.

Furthermore, the demand for broadcast space in the United States and Mexico depends on the needs of television and radio broadcasters. Among other things, technological advances, including the development of satellite-delivered radio and video services, may reduce the need for tower-based broadcast transmission. In addition, any significant increase in attrition rate or decrease in overall demand for broadcast space could have a material adverse effect on our business, results of operations or financial condition.

If our tenants share site infrastructure to a significant degree or consolidate or merge, our growth, revenue and ability to generate positive cash flows could be materially and adversely affected.

Extensive sharing of site infrastructure, roaming or resale arrangements among wireless service providers as an alternative to leasing our communications sites without compensation to us may cause new lease activity to slow if carriers utilize shared equipment rather than deploy new equipment, or may result in the decommissioning of equipment on certain existing sites because portions of the tenants’ networks may become redundant. In addition, significant consolidation among our tenants may materially and adversely affect our growth and revenues. For example, in the United States, recentlyCertain combined companies have either rationalized or announced plans to rationalize duplicative parts of their networks which may result in the decommissioning of certain equipment on our communications sites. We would expect a similar outcome in certain other countries where we do business if consolidation of certain tenants occurs. In addition, certain combined companies haveor modernized or are currently modernizing their networks, and these and other tenants could determine not to renew leases with us as a result. Our ongoing contractual revenues and our future results may be negatively impacted if a significant number of these leases are not renewed.

Increasing competition for tenants in the tower industry may materially and adversely affect our pricing.

Our industry is highly competitive and our tenants have numerous alternatives in leasing antenna space. Competitive pricing for tenants on towers from competitors could materially and adversely affect our lease rates.

We may not be able to renew existing tenant leases or enter into new tenant leases, or if we are able to renew or enter new leases, it may be at rates lower than our current rates, resulting in a material adverse impact on our results of operations and growth rate. In addition, should inflation rates exceed our fixed escalator percentages in markets where the majority of our leases include fixed escalators, our income would be adversely affected. Increasing competition for tenants or significant increases in inflation rates could materially and adversely affect our business, results of operations or financial condition.

Competition for assets could adversely affect our ability to achieve our return on investment criteria.

We may experience increased competition, which could make the acquisition of high quality assets significantly more costly. Some of our competitors are larger and may have greater financial resources than we do, while other competitors may apply lower investment criteria than we do. In addition, we may not anticipate increased competition entering a particular market or competing for the same assets. Higher prices for assets could make it more difficult to achieve our return on investment criteria, which could materially and adversely affect our business, results of operations or financial condition.

Our business is subject to government regulations and changes in current or future laws or regulations could restrict our ability to operate our business as we currently do.

Our business and that of our tenants are subject to federal, state, local and foreign regulations. In certain jurisdictions, these regulations could be applied or enforced retroactively.retroactively, which could require that we modify or dismantle an existing tower. Zoning authorities and community organizations are often opposed to the construction in their communities, which can delay, prevent or increase the cost of new tower construction, modifications, additions of new antennas to a site or site upgrades, thereby limiting our ability to respond to tenant demands and requirements. In addition, in certain foreign jurisdictions, we are required to pay annual license fees, and these fees may be subject to substantial increases by the government. Foreign jurisdictions in which we operate and currently are not required to pay license fees may enact license fees, which may apply retroactively. In certain foreign jurisdictions, there may be changes to zoning regulations or construction laws based on site location, which may result in increased costs to modify certain of our existing towers or decreased revenue due to the removal of certain towers to ensure compliance with such changes. Existing regulatory policies may materially and adversely affect the associated timing or cost of suchconstruction projects associated with our communications sites and additional regulations may be adopted that increase delays or result in additional costs to us, or that prevent such projects in certain locations. Furthermore, the tax laws, regulations and interpretations governing REITs may change at any time.time, perhaps with retroactive effect. In addition, some of these changes could have a more significant impact on us as compared to other REITs due to the nature of our business and our use of TRSs. These factors could materially and adversely affect our business, results of operations or financial condition. Furthermore, some foreign jurisdictions have implemented regulations governing investment funds or their managers, which may be interpreted to apply to REITs, and there is uncertainty as to the interpretation and implementation of these regulations.

Our leverage and debt service obligations may materially and adversely affect us.

As of December 31, 2013, we had approximately $14.5 billion of consolidated debt and the ability to borrow additional amounts of approximately $2.0 billion under our credit facilities, net of any outstanding letters of credit. Our leverage could render us unable to generate cash sufficient to pay when due the principal of,

interest on, or other amounts due with respect to, our indebtedness. We are also permitted, subject to certain restrictions under our existing indebtedness, to draw down on our credit facilities and obtain additional long-term debt and working capital lines of credit to meet future financing needs.

Our leverage could have significant negative consequences onto our business, results of operations or financial condition, including:

In addition, to meet the REIT distribution requirements and maintain our qualification and taxation as a REIT, we may need to borrow funds, even if the then-prevailing market conditions are not favorable, and the REIT distribution requirements may increase the financing we need to fund capital expenditures, future growth and expansion initiatives. This would increase our total leverage.

Increasing competition inFailure to successfully and efficiently integrate acquired or leased assets, including from the tower industryProposed Verizon Transaction (the “Verizon Assets”), into our operations may materially and adversely affect us.our business, operations and financial condition.

WeIntegrating acquired portfolios of communications sites may experience increased competition, which could makerequire significant resources, as well as attention from our management team. In addition, we may incur certain non-recurring charges associated with the acquisitionintegration of high qualityacquired or leased assets significantly more costly. Some ofor businesses into our competitors, such as wireless carriers that allow collocation on their towers, are larger and may have greater financial resources than we do, while other competitors may have lower return on investment criteria than we do.

Our industry is highly competitive and our tenants have numerous alternatives in leasing antenna space. Competitive pricing for tenants on towers from competitorsoperations. Further, the significant acquisition-related integration costs could materially and adversely affect our results of operations in the period in which such charges are recorded or our cash flow in the period in which any related costs are actually paid. For example, the integration of the Verizon Assets, which includes up to 11,489 towers, into our operations will be a significant undertaking, and we anticipate that we will incur certain non-recurring charges associated with the integration of the Verizon Assets into our operations, including costs for tasks such as tower visits and audits and ground and tenant lease ratesverifications. Additional integration challenges include:

Additionally, we may fail to successfully integrate the assets we acquire or fail to utilize such assets to their full capacity. If we are not able to meet these integration challenges, we may not be able to renew existing tenant leases or enter into new tenant leases, resulting in a material adverse impact onrealize the benefits we expect from our acquired portfolios and businesses, including the Proposed Verizon Transaction, and our business, financial condition and results of operations and growth rate.will be adversely affected.

The higher prices for assets, combined with the competitive pricing pressure on tenant leases, could make it more difficult to achieve our return on investment criteria. Increasing competition for either tower assets or tenants could materially and adversely affect our business, results of operations or financial condition.

Our expansion initiatives involve a number of risks and uncertainties that could adversely affect our operating results, disrupt our operations or expose us to additional risk if we are not able to successfully integrate operations, assets and personnel.risk.

As we continue to acquire communications sites in our existing markets and expand into new markets, we are subject to a number of risks and uncertainties, including not meeting our return on investment criteria and

financial objectives, increased costs, assumed liabilities and the diversion of managerial attention due to acquisitions. Achieving the benefits of acquisitions depends in part on timely and efficiently integrating operations, communications tower portfolios and personnel. Integration may be difficult and unpredictable for many reasons, including, among other things, differing systems and processes, cultural differences, customary business practices and conflicting policies, procedures and operations. In addition, integrating businesses may significantly burden management and internal resources, including the potential loss or unavailability of key personnel.

Furthermore, our international expansion initiatives are subject to additional risks such as complex laws, regulations and business practices thatthose described in the risk factor immediately below, some of which may require additional resources and personnel,personnel.

In addition, as a result of prior acquisitions, we have a substantial amount of intangible assets and goodwill. In accordance with accounting principles generally accepted in the United States (“GAAP”), we are required to assess our goodwill and other intangible assets annually or more frequently in the event of circumstances indicating potential impairment to determine if they are impaired. If the testing performed indicates that an asset may not be recoverable, we are required to record a non-cash impairment charge for the difference between the carrying value of the goodwill or other intangible assets and the implied fair value of the goodwill or the estimated fair value of other risks described immediately belowintangible assets in “—the period the determination is made.

Our foreign operations are subject to economic, political and other risks that could materially and adversely affect our revenues or financial position, including risks associated with fluctuations in foreign currency exchange rates.” As a result, our foreign operations and expansion initiatives may not succeed andbe successful or we may materially and adversely affectbe required to record impairment charges for our goodwill or for other intangible assets, which could have a material adverse effect on our business, results of operations or financial condition.

Our foreign operations are subject to economic, political and other risks that could materially and adversely affect our revenues or financial position, including risks associated with fluctuations in foreign currency exchange rates.

Our international business operations and our expansion into new markets in the future could result in adverse financial consequences and operational problems not typically experienced in the United States. For the year ended December 31, 2013, approximately 33% of our consolidated revenue was generated by our international operations, compared to 30% for the year ended December 31, 2012. We anticipate that our revenues from our international operations will continue to grow. Accordingly, our business is subject to risks associated with doing business internationally, including:

We also face risks associated with changes in foreign currency exchange rates, including those arising from our operations, investments and financing transactions related to our international business. Volatility in foreign currency exchange rates can also affect our ability to plan, forecast and budget for our international operations and expansion efforts. Our revenues earned from our international operations are primarily denominated in their respective local currencies. We have not historically engaged in significant currency hedging activities relating to our non-U.S. Dollar operations, and a weakening of these foreign currencies against the U.S. Dollar would negatively impact our reported revenues, operating profits and income.

In our international operations, many of our tenants are subsidiaries of global telecommunications companies. These subsidiaries may not have the explicit or implied financial support of their parent entities.

In addition, as we continue to invest in joint venture opportunities internationally, our partners may have business or economic goals that are inconsistent with ours, be in positions to take action contrary to our interests, policies or objectives, have competing interests in our, or other, markets that could create conflict of interest issues, withhold consents contrary to our requests or become unable or unwilling to fulfill their commitments, any of which could expose us to additional liabilities or costs, including requiring us to assume and fulfill the obligations of that joint venture.

A substantial portion of our revenue is derived from a small number of tenants, and we are sensitive to changes in the creditworthiness and financial strength of our tenants.

A substantial portion of our total operating revenues is derived from a small number of tenants. For the year ended December 31, 2013, four tenants accounted for approximately 83% of our domestic rental and management segment revenue; and five tenants accounted for approximately 55% of our international rental and management segment revenue. If any of these tenants is unwilling or unable to perform its obligations under our agreements with it, our revenues, results of operations, financial condition and liquidity could be materially and adversely affected. In the ordinary course of our business, we do occasionally experience disputes with our tenants, generally regarding the interpretation of terms in our leases. WeHistorically, we have historically resolved these disputes in a manner that did not have a material adverse effect on us or our tenant relationships. However, it is possible that such disputes could lead to a termination of our leases with tenants or a material modification of the terms of those leases, either of which could have a material adverse effect on our business, results of operations or financial condition. If we are forced to resolve any of these disputes through litigation, our relationship with the applicable tenant could be terminated or damaged, which could lead to decreased revenue or increased costs, resulting in a corresponding adverse effect on our business, results of operations or financial condition.

Additionally, dueDue to the long-term nature of our tenant leases, we depend on the continued financial strength of our tenants. Many wireless service providers operate with substantial leverage. Sometimes our tenants, or their parent companies, face financial difficulty or file for bankruptcy.

In addition, many of our tenants and potential tenants rely on capital raising activities to fund their operations and capital expenditures. Downturnsexpenditures, which may be more difficult or expensive in the event of downturns in the economy andor disruptions in the financial and credit markets have periodically made it more difficult and more expensive to raise capital.markets. If our tenants or potential tenants are unable to raise

adequate capital to fund their business plans, they may reduce their spending, which could materially and adversely affect demand for our communications sites and our network development services business. If, as a result of a prolonged economic downturn or otherwise, one or more of our significant tenants experienced financial difficulties or filed for bankruptcy, it could result in uncollectible accounts receivable and an impairment of our deferred rent asset, tower asset, network location intangible asset or customer-related intangible asset. The loss of significant tenants, or the loss of all or a portion of our anticipated lease revenues from certain tenants, could have a material adverse effect on our business, results of operations or financial condition.

We may fail to realize the growth prospects and cost savings anticipated as a result of, and will incur significant transaction and acquisition-related integration costs in connection with, our acquisition of MIPT.

The success of the acquisition of MIPT will depend, in part, on our ability to realize the anticipated business opportunities and growth prospects from combining our business with those of MIPT. We may never realize

these business opportunities and growth prospects, or we may encounter unanticipated accounting, internal control, regulatory or compliance problems.

In addition, we and MIPT have operated independently. As a result, there may be a disruption of each company’s ongoing businesses, tax costs or inefficiencies, or inconsistencies in standards, controls, information technology systems, procedures and policies, any of which could adversely affect our ability to maintain relationships with tenants, employees or other third parties or our ability to achieve the anticipated benefits of the acquisition and could harm our financial performance. We anticipate that we will incur certain non-recurring charges in connection with integrating MIPT, including severance and charges associated with integrating process and systems. We currently cannot identify the timing, nature and amount of all such charges. Further, the significant acquisition-related integration costs could materially adversely affect our results of operations in the period in which such charges are recorded or our cash flow in the period in which any related costs are actually paid. Although we believe that the elimination of duplicative costs, as well as the realization of other efficiencies related to this integration, will offset incremental transaction and acquisition-related costs over time, this net benefit may not be achieved in the near term, or at all. We also expect to incur costs to implement such efficiencies. In that regard, because MIPT is a private company, we may be required to improve MIPT’s internal controls, procedures and policies to meet standards applicable to public companies, which may be time-consuming and more expensive than anticipated.

New technologies or changes in a tenant’s business model could make our tower leasing business less desirable and result in decreasing revenues.

The development and implementation of new technologies designed to enhance the efficiency of wireless networks or changes in a tenant’s business model could reduce the need for tower-based wireless services, decrease demand for tower space or reduce previously obtainable lease rates. In addition, tenants may have less of their budgets allocated to lease space on our towers, as the industry is trending towards deploying increased capital to the development and implementation of new technologies. Examples of these technologies include spectrally efficient technologies, which could relieve a portion of our tenants’ network capacity needs and as a result, could reduce the demand for tower-based antenna space. Additionally, certain small cell complementary network technologies could shift a portion of our tenants’ network investments away from the traditional tower-based networks, which may reduce the need for carriers to add more equipment at certain communications sites. Moreover, the emergence of alternative technologies could reduce the need for tower-based broadcast services transmission and reception. For example, the growth in the delivery of wireless communications, radio and video services by direct broadcast satellites could materially and adversely affect demand for our tower space. Further, a tenant may decide to no longer outsource tower infrastructure or otherwise change its business model, which would result in a decrease in our revenue. The development and implementation of any of these and similar technologies to any significant degree or changes in a tenant’s business model could have a material adverse effect on our business, results of operations or financial condition.

If we fail to remain qualified as a REIT, we will be subject to tax at corporate income tax rates, which may substantially reduce funds otherwise available.

Effective for the taxable year beginning January 1, 2012, we began operating as a REIT for federal income tax purposes. If we fail to remain qualified as a REIT, we will be taxed at corporate income tax rates unless certain relief provisions apply.

Qualification as a REIT requires the application of certain highly technical and complex provisions of the Internal Revenue Code of 1986, as amended (the “Code”), which provisions may change from time to time, to our operations as well as various factual determinations concerning matters and circumstances not entirely within our control. Further, tax reform proposals, if enacted, may adversely affect our ability to remain qualified as a REIT or the benefits of remaining so qualified. There are limited judicial or administrative interpretations of the relevant provisions of the Code.

If, in any taxable year, we fail to qualify for taxation as a REIT and are not entitled to relief under the Code:

Any corporate tax liability could be substantial and would reduce the amount of cash available for other purposes. If we fail to qualify for taxation as a REIT, we may need to borrow additional funds or liquidate some

investments to pay any additional tax liability. Accordingly, funds available for investment, operations and operationsdistribution would be reduced.

Furthermore, as a result of our acquisition of MIPT,MIP Tower Holdings LLC (“MIPT”), we own an interest in a subsidiary REIT. The subsidiary REIT is independently subject to, and must comply with, the same REIT requirements that we must satisfy in order to qualify as a REIT, together with all other rules applicable to REITs. If the subsidiary REIT fails to qualify as a REIT, and certain relief provisions do not apply, then (i) the subsidiary REIT would become subject to federal income tax, (ii) the subsidiary REIT will be disqualified from treatment as a REIT for the four taxable years immediately following the year during which qualification was lost, (iii) our ownership of shares in such subsidiary REIT will cease to be a qualifying asset for purposes of the asset tests applicable to REITs and any dividend income or gains derived by us from such subsidiary REIT may cease to be treated as income that qualifies for purposes of the 75% gross income test and (iv) we may fail certain of the asset tests applicable to REITs, in which event we will fail to qualify as a REIT unless we are able to avail ourselves of certainspecified relief provisions.

We may be limited in our ability to fund required distributions using cash generated through our TRSs.

As a REIT, we must distribute to our stockholders an amount equal to at least 90% of the REIT taxable income (determined before the deduction for distributed earnings and excluding any net capital gain). Our ability to receive distributions from our TRSs to fund these distributions is limited by the rules with which we must comply to maintain our status as a REIT. In particular, at least 75% of our gross income for each taxable year as a REIT must be derived from real estate, which principally includes gross income from the leasing of our communications sites and qualified rental-related services. Consequently, no more than 25% of our gross income may consist of dividend income from our TRSs and other non-qualifying types of income. Thus, our ability to receive distributions from our TRSs may be limited and may impact our ability to fund distributions to our stockholders.

In addition, the majority of our income and cash flows from our TRSs are generated from our international operations. In many cases, there are local withholding taxes and currency controls that may impact our ability or willingness to repatriate funds to the United States to help satisfy REIT distribution requirements.

Complying with REIT requirements may limit our flexibility or cause us to forego otherwise attractive opportunities.

Our use of TRSs enables us to engage in non-REIT qualifying business activities. Under the Code, no more than 25% of the value of the assets of a REIT may be represented by securities of one or more TRSs and other non-qualifying assets. This limitation may hinder our ability to make certain attractive investments, including the purchase of non-qualifying assets, the expansion of non-real estate activities and investments in the businesses to be conducted by our TRSs, and to that extent limit our opportunities and our flexibility to change our business strategy.

Specifically, this limitation may affect our ability to make additional investments in our managed networks business or network development services segment as currently structured and operated, in other non-REIT qualifying operations or assets, or in international operations conducted through TRSs that we do not elect to bring into the REIT structure. Further, acquisition opportunities in domestic and international markets may be

adversely affected if we need or require the target company to comply with certain REIT requirements prior to closing.

In addition,Further, as a REIT, we must distribute to our stockholders an amount equal to at least 90% of the REIT taxable income (determined before the deduction for distributed earnings and excluding any net capital gain). To meet our annual distribution requirements, we may be required to distribute amounts that may otherwise be used for our operations, including amounts that may otherwise be invested in future acquisitions, capital expenditures or repayment of debt,debt. As no more than 25% of our gross income may consist of dividend income from our TRSs and it is possible that we mightother non-qualifying types of income, our ability to receive distributions from our TRSs may be required to borrow funds, sell assets or raise equitylimited and may impact our ability to fund these distributions even ifto our stockholders or to use income of our TRSs to fund other investments.

In addition, the then-prevailing market conditionsmajority of our income and cash flows from our TRSs are not favorable for these borrowings, salesgenerated from our international operations. In many cases, there are local withholding taxes and currency controls that may impact our ability or offerings.willingness to repatriate funds to the United States to help satisfy REIT distribution requirements.

Certain of our business activities may be subject to corporate level income tax and foreign taxes, which reduce our cash flows and may create deferred and contingent tax liabilities.

We are subject to certain federal, state, local and foreign taxes on our income and assets, including alternative minimum taxes, taxes on any undistributed income and state, local or foreign income, franchise, property and transfer taxes. Any of these taxes would decrease our earnings and our available cash.

We are also subject to the continuous examination of our income tax returns by the U.S. Internal Revenue Service and state, local and foreign tax authorities. The results of an audit and examination of previously filed tax returns and continuing assessments of our tax exposures may have an adverse effect on our provision for income taxes and cash tax liability.

Our TRS assets and operations will continue to be subject, as applicable, to federal and state corporate income taxes and to foreign taxes in the jurisdictions in which those assets and operations are located.

We may need additional financing to fund capital expenditures, future growth and expansion initiatives and to satisfy our REIT distribution requirements.

To fund capital expenditures, future growth and expansion initiatives and to satisfy our REIT distribution requirements, we may need to raise additional capital through financing activities, sell assetsasset sales or raise equity.equity issuances. We believe our cash provided by operations for the year ending December 31, 2014 will sufficiently fund our cash needs for operations, capital expenditures, required REIT distribution payments and cash debt service (interest and principal repayments) obligations through 2014. However, we anticipate that we may need to obtain additional sources of capital in the future to fund capital expenditures, future growth and expansion initiatives and satisfy our REIT distribution requirements. Depending on market conditions, we may seek to raise capital through credit facilities or debt or equity offerings. An increase in our outstanding debt could lead to a downgrade of our credit rating. A downgrade of our credit rating below investment grade could negatively impact our ability to access credit markets or preclude us from obtaining funds on investment grade terms and conditions. Further, certain of our current debt instruments limit the amount of indebtedness we and our subsidiaries may incur. Additional financing, therefore, may be unavailable, more expensive or restricted by the terms of our outstanding indebtedness. If we are unable to raise capital when our needs arise, we may not be able to fund our capital expenditures, future growth and expansion initiatives or satisfy our REIT distribution requirements.

If we are unable to protect our rights to the land under our towers, it could adversely affect our business and operating results.

Our real property interests relating to our towers consist primarily of leasehold and sub-leasehold interests, fee interests, easements, licenses and rights-of-way. A loss of these interests at a particular tower site may interfere with our ability to operate a tower and generate revenues. For various reasons, we may not always have the ability to access, analyze and verify all information regarding titles and other issues prior to completing an acquisition of communications sites, which can affect our rights to access and operate a site. From time to time we also experience disputes with landowners regarding the terms of ground agreements for land under towers, which can affect our ability to access and operate tower sites. Further, for various reasons, landowners may not want to renew their ground agreements with us, they may lose their rights to the land, or they may transfer their land interests to third parties, including ground lease aggregators, which could affect our ability to renew ground agreements on commercially viable terms. Approximately 88%A significant number of the communications sites in our portfolio as of December 31, 2013 are located on land we lease pursuant to operating leases. Approximately 74% ofleases, and the ground

leases for these sites have a final expiration date of 20232024 and beyond. Further, for various reasons, title to property interests in some of the foreign jurisdictions in which we operate may not be as certain as title to our property interests in the United States. Our inability to protect our rights to the land under our towers may have a material adverse effect on our business, results of operations or financial condition.

If we are unable or choose not to exercise our rights to purchase towers that are subject to lease and sublease agreements at the end of the applicable period, our cash flows derived from such towers will be eliminated.

Our communications real estate portfolio includes towers that we operate pursuant to lease and sublease agreements that include a purchase option at the end of each lease period. We may not have the required available capital to exercise our right to purchase leased or subleased towers at the end of the applicable period, or we may choose, for business or other reasons, not to exercise our right to purchase such towers. In the event that we do not exercise these purchase rights, or are otherwise unable to acquire an interest that would allow us to continue to operate these towers after the applicable period, we will lose the cash flows derived from such

towers. In the event that we decide to exercise these purchase rights, the benefits of the acquisitions of a significant number of towers may not exceed the associated acquisition, compliance and integration costs, which could have a material adverse effect on our business, results of operations or financial condition.

Restrictive covenants in the agreements related to our securitization transactions, our credit facilities and our debt securities could materially and adversely affect our business by limiting flexibility.flexibility, and we may be prohibited from paying dividends on our common stock if we fail to pay scheduled dividends on our preferred stock, which may jeopardize our qualification for taxation as a REIT.

The agreements related to our securitization transactions include operating covenants and other restrictions customary for loans subject to rated securitizations. Among other things, the borrowers under the agreements are prohibited from incurring other indebtedness for borrowed money or further encumbering their assets. A failure to comply with the covenants in the agreements could prevent the borrowers from taking certain actions with respect to the secured assets and could prevent the borrowers from distributing any excess cash from the operation of such assets to us. If the borrowers were to default on any of the loans, the servicer on such loan could seek to foreclose upon or otherwise convert the ownership of the secured assets, in which case we could lose such assets and the cash flow associated with such assets.

The agreements for our credit facilities also contain restrictive covenants as well as requirements to comply with certainand leverage and other financial maintenance tests andthat could thus limit our ability to take various actions, including incurring additional debt, guaranteeing indebtedness or making distributions to stockholders, and engaging in various types of transactions, including mergers, acquisitions and sales of assets. Additionally, our debt agreements restrict our and our subsidiaries’ ability to incur liens securing our or their indebtedness. These covenants could have an adverse effect on our business by limiting our ability to take advantage of financing, new tower development, mergers and acquisitions or other opportunities. Further, ifIf these limits prevent us from satisfying our REIT distribution requirements, we could fail to qualify for taxation as a REIT. IfEven if these limits do not jeopardize our qualification for taxation as a REIT, but neverthelessthey may prevent us from distributing 100% of our REIT taxable income, we will bemaking us subject to federal corporate income tax, and potentially a nondeductible excise tax, on the retained amounts.

In addition,Further, reporting and information covenants in our credit agreements and indentures require that we provide financial and operating information within certain time periods. If we are unable to timely provide the required information, we would be in breach of these covenants. For more information regarding the covenants and requirements discussed above, please see Item 7 of this Annual Report under the caption “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Liquidity and Capital Resources—Factors Affecting Sources of Liquidity” and note 8 to our consolidated financial statements included in this Annual Report.

WeFurther, the terms of our preferred stock provide that, unless full cumulative dividends have been paid or set aside for payment on all outstanding preferred stock for all prior dividend periods, no dividends may incur goodwillbe declared or paid on our common stock. A failure to pay dividends on both our preferred and other intangible asset impairment charges, which could result inour common stock might jeopardize our qualification for taxation as a significant reductionREIT for federal income tax purposes. For more information on the terms of our preferred stock, see note 16 to our earnings.

In accordance with accounting principles generally acceptedconsolidated financial statements included in the United States (“GAAP”), we are required to assess our goodwill and other intangible assets annually or more frequently in the event of circumstances indicating potential impairment to determine if they are impaired. These circumstances could include a decline in our actual or expected future cash flows or income, a significant adverse change in the business climate, a decline in market capitalization, or slower growth rates in our industry, among others. If the testing performed indicates that an asset may not be recoverable, we are required to record a non-cash impairment charge for the difference between the carrying value of the goodwill or other intangible assets and the implied fair value of the goodwill or other intangible assets in the period the determination is made.

It is possible that in the future, we may be required to record impairment charges for our goodwill or for other intangible assets. These charges could be significant, which could have a material adverse effect on our business, results of operations or financial condition.this Annual Report.

Our costs could increase and our revenues could decrease due to perceived health risks from radio emissions, especially if these perceived risks are substantiated.

Public perception of possible health risks associated with cellular and other wireless communications technology could slow the growth of wireless companies, which could in turn slow our growth. In particular, negative public perception of, and regulations regarding, these perceived health risks could undermine the market acceptance of wireless communications services and increase opposition to the development and expansion of tower sites. The potential connection between radio frequency emissions and certain negative health or environmental effects has been the subject of substantial study by the scientific community in recent years and numerous health-related lawsuits have been filed against wireless carriers and wireless device manufacturers. If a scientific study or court decision resulted in a finding that radio frequency emissions pose health

risks to consumers, it could negatively impact our tenants and the market for wireless services, which could materially and adversely affect our business, results of operations or financial condition. We do not maintain any significant insurance with respect to these matters.

We could have liability under environmental and occupational safety and health laws.

Our operations are subject to the requirements of various federal, state, local and foreign environmental and occupational safety and health laws and regulations, including those relating to the management, use, storage, disposal, emission and remediation of, and exposure to, hazardous and non-hazardous substances, materials and wastes. As the owner, lessee or operator of real property and facilities, we may be liable for substantial costs of investigation, removal or remediation of soil and groundwater contaminated by hazardous materials, and for damages and costs relating to off-site migration of hazardous materials, without regard to whether we, as the owner, lessee or operator, knew of, or were responsible for, the contamination. We may also be liable for certain costs of remediating contamination at third-party sites to which we sent waste for disposal, even if the original disposal may have complied with all legal requirements at the time. Many of these laws and regulations contain information reporting and record keeping requirements. We cannot assure you that we aremay not be at all times in complete compliance with all environmental requirements. We may be subject to potentially significant fines or penalties if we fail to comply with any of these requirements. The requirements of these laws and regulations are complex, change frequently and could become more stringent in the future. In certain jurisdictions these laws and regulations could be applied or enforced retroactively. It is possible that these requirements will change or that liabilities will arise in the future in a manner that could have a material adverse effect on our business, results of operations or financial condition.

Our towers, or data centers or computer systems may be affected by natural disasters and other unforeseen events for which our insurance may not provide adequate coverage.

Our towers are subject to risks associated with natural disasters, such as ice and wind storms, tornadoes, floods, hurricanes and earthquakes, as well as other unforeseen events.events, such as acts of terrorism. Any damage or destruction to our towers or data centers, or certain unforeseen events, may impact our ability to provide services to our tenants.

As part of our normal business activities, we rely on information technology and other computer resources to carry out important operational activities and to maintain our business records. Our computer systems could fail on their own accord and are subject to interruption or damage from power outages, computer and telecommunications failures, computer viruses, security breaches (including through cyber attack and data theft), usage errors, catastrophic events such as natural disasters and other events beyond our control. Although we have disaster recovery programs and security measures in place, if our computer systems and our backup systems are compromised, degraded, damaged, or breached, or otherwise cease to function properly, we could suffer interruptions in our operations or unintentionally allow misappropriation of proprietary or confidential information (including information about our tenants or landlords), which could damage our reputation and require us to incur significant costs to remediate or otherwise resolve these issues.

While we maintain insurance coverage for natural disasters, we may not have adequate insurance to cover the associated costs of repair or reconstruction for a major future event. Further, we carry business interruption insurance, but our insurance may not adequately cover all of our lost revenues,revenue, including potential revenues from new tenants that could have been added to our towers but for the event. If we are unable to provide services to our tenants, it could lead to tenant loss, resulting in a corresponding material adverse effect on our business, results of operations or financial condition.

None.

Details of each of our principal offices as of December 31, 20132014 are provided below:

In addition to the principal offices set forth above, we maintain offices in the geographic areas we serve through which we operate our tower leasing and services businesses, as well as maintain offices toan office through which we pursue international business development initiatives. We believe that our owned and leased facilities are suitable and adequate to meet our anticipated needs.

As of December 31, 2013,2014, we owned and operated a portfolio of 67,41875,594 communications sites in the United States, Brazil, Chile, Colombia, Costa Rica, Germany, Ghana, India, Mexico, Panama, Peru, South Africa and Uganda. In November 2014, we signed an agreement to acquire communications sites in Nigeria. See the table in Item 7 of this Annual Report, under the caption “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Executive Overview” for more detailed information on the geographic locations of our communications sites. In addition, we own property interests that we lease to communications service providers and third-party tower operators in the United States, which are included in our domestic rental and management segment.

Domestic Rental and Management Segment. Our interests in our domestic communications sites are comprised of a variety of ownership interests, including leases created by long-term ground lease agreements,

easements, licenses or rights-of-way granted by government entities. Pursuant to the loan agreement for the Securitization, thesecuritization transaction completed in March 2013 (the “Securitization”), 5,195 towers in the United States subject to the Securitization transaction as of December 31, 2013, are subject to mortgages, deeds of trust and deeds to secure the loan.loan as of December 31, 2014. In addition, 1,4701,517 property interests in the United States are subject to mortgages and deeds of trust to secure three separate classes of Secured Cellular Site Revenue Notes (the “Unison Notes”) assumed in connection with the acquisition of certain legal entities from Unison Holdings LLC and Unison Site Management II, L.L.C. (the “Unison Acquisition”). In connection with our acquisition of MIPT, a private REIT and parent company to Global Tower Partners (“GTP”), we assumed approximately $1.49 billion principal amount of existing indebtedness under six series, consisting of eleven separate classes, of Secured Tower Revenue Notes issued by certain subsidiaries of GTP in several securitization transactions, of which we repaid one series, consisting of two classes, in August 2014 (the remaining notes, the “GTP Notes”). The GTP Notes are secured by, among other things, 3,8932,845 towers and 1,7171,035 property interests and other related assets.

A typical domestic tower site consists of a compound enclosing the tower site, a tower structure and one or more equipment shelters that house a variety of transmitting, receiving and switching equipment. The principal types of our domestic towers are guyed, self-supporting lattice and monopole.

International Rental and Management Segment. Our interests in our international communications sites are comprised of a variety of ownership interests, including leases created by long-term ground lease agreements, easements, licenses or rights-of-way granted by private or government entities. Our financings in Colombia Costa Rica and South Africa are secured by an aggregate of 2,1485,220 towers.

A typical international tower site consists of a compound enclosing the tower site, a tower structure, backup or auxiliary power generators and batteries and one or more equipment shelters that house a variety of transmitting, receiving and switching equipment. The four principal types of our international towers are guyed, self-supporting lattice, monopole and rooftop. Guyed, self-supporting lattice and monopole structures are similar to those in our domestic segment. Rooftop towers are primarily used in metropolitan areas, where locations for traditional tower structures are unavailable. Rooftop towers typically have heights ranging from 10 to 100 feet.

Ground Leases.Of the 67,06975,164 towers in our portfolio as of December 31, 2013,2014, approximately 88% were located on land we lease. Domestically,Typically, we seek to enter ground leases for land under our towers generally have a termwith terms of approximately twenty to twenty-five years, which isare comprised of an initial termterms of approximately five years with three or four automatic five-year renewal periods. Internationally, ground leases, or similar agreements that grant use rights for land underlying our towers, typically also have a term of approximately twenty to twenty-five years, which is comprised of an initial term ranging from five to ten years with one or more automatic or exercisable renewal periods. As a result, approximately 74%70% of the ground agreements for our sites have a final expiration date of 20232024 and beyond.

Tenants. Our tenants are primarily wireless service providers, broadcasters and other communications service providers. As of December 31, 2013,2014, our four top tenants by total revenue were AT&T Mobility (18%(20%), Sprint Nextel (16%(15%), Verizon Wireless (11%) and T-Mobile USA (11%(10%). In general, our tenant leases have an initial non-cancellable term of five to ten years, with multiple five-year renewal terms. As a result, approximately 71% of our current tenant leases have a renewal date of 20192020 or beyond.

We are involved in several lawsuits against TriStar Investors LLP and its affiliates (“TriStar”) in various states regarding single tower sites where TriStar has taken land interests under our owned or managed sites and we believe TriStar has improperly induced the landowner to breach obligations to us. In addition, on February 16, 2012, TriStar brought a federal action against us, in the United States District Court for the Northern District of Texas, in which TriStar principally alleges that we made misrepresentations to landowners when competing with TriStar for land under our owned or managed sites. On January 22, 2013, we filed an amended answer and counterclaim against TriStar and certain of its employees, denying Tristar’s claims and asserting that TriStar has engaged in a pattern of unlawful activity, including: (i) entering into agreements not to compete for land under certain towers; and (ii) making widespread misrepresentations to landowners regarding both TriStar and us. TriStar and the Company are each seeking injunctive relief that would prohibit the other party from making certain statements when interacting with landowners, as well as damages.

We periodically become involved in various claims and lawsuits that are incidental to our business. In the opinion of management, after consultation with counsel, other than the legal proceeding discussed above and in note 19 to our consolidated financial statements included in this Annual Report, there are no matters currently pending that would, in the event of an adverse outcome, have a material impact on our consolidated financial position, results of operations or liquidity.

N/A.

PART II

The following table presents reported quarterly high and low per share sale prices of our common stock on the NYSE for the years 20132014 and 2012.2013.

On February 14, 2014,13, 2015, the closing price of our common stock was $83.20$96.40 per share as reported on the NYSE. As of February  14, 2014,13, 2015, we had 395,017,519396,708,636 outstanding shares of common stock and 176166 registered holders.

Dividends

As a REIT, we must annually distribute to our stockholders an amount equal to at least 90% of our REIT taxable income (determined before the deduction for distributed earnings and excluding any net capital gain). Generally, we have distributed and expect to continue to distribute all or substantially all of our REIT taxable income so asafter taking into consideration our net operating loss carryforwards (“NOLs”).

In May 2014 we issued the Mandatory Convertible Preferred Stock and subsequently began paying dividends pursuant to not be subject to income tax or excise taxthe terms thereof. For more information on undistributed REIT taxable income. the Mandatory Convertible Preferred Stock, see Item 7 of this Annual Report under the caption “Management’s Discussion and Analysis of Financial Condition and Results of Operations—Liquidity and Capital Resources.”

The amount, timing and frequency of future distributions will be at the sole discretion of our Board of Directors and will be declared based upon various factors, a number of which may be beyond our control, including our financial condition and operating cash flows, the amount required to maintain our qualification for taxation as a REIT status and reduce any income and excise taxes that we otherwise would be required to pay, limitations on distributions in our existing and future debt and preferred equity instruments, our ability to utilize net operating losses (“NOLs”)NOLs to offset our distribution requirements, limitations on our ability to fund distributions using cash generated through our TRSs and other factors that our Board of Directors may deem relevant.

Since our conversion to a REIT in 2012, we have distributed an aggregate of approximately $1.3 billion to our common stockholders, including approximately $150.7 million paid in January 2015. These distributions are primarily taxed as ordinary income.

During the year ended December 31, 2014, we declared the following cash distributions:

During the year ended December 31, 2013, we declared and paid the following regular cash distributions to our stockholders:distributions:

During the year ended December 31, 2012, we declared and paid the following regular cash distributions to our stockholders:

Declaration Date		Payment Date				Record Date				Distribution per share				Aggregate  Payment Amount (in millions)
Common Stock
March 12, 2013			April 25, 2013				April 10, 2013			$	0.26			$	102.8
May 22, 2013			July 16, 2013				June 17, 2013			$	0.27			$	106.7
September 12, 2013			October 7, 2013				September 23, 2013			$	0.28			$	110.5
December 4, 2013			December 31, 2013				December 16, 2013			$	0.29			$	114.5

Performance Graph

This performance graph is furnished and shall not be deemed ‘‘filed’’ with the SEC or subject to Section 18 of the Exchange Act, nor shall it be deemed incorporated by reference in any of our filings under the Securities Act of 1933, as amended.

The following graph compares the cumulative total stockholder return on our common stock with the cumulative total return of the S&P 500 Index, the Dow Jones U.S. Telecommunications Equipment Index and the FTSE NAREIT All Equity REITs Index. The performance graph assumes that on December 31, 2008,2009, $100 was invested in each of our common stock, the S&P 500 Index, the Dow Jones U.S. Telecommunications Equipment Index and the FTSE NAREIT All Equity REITs Index. The cumulative return shown in the graph assumes reinvestment of all dividends. The performance of our common stock reflected below is not necessarily indicative of future performance.

ITEM 6.

SELECTED FINANCIAL DATA

The selected financial data should be read in conjunction with our “Management’s Discussion and Analysis of Financial Condition and Results of Operations,” and our audited consolidated financial statements and the related notes to those consolidated financial statements included in this Annual Report.

Year-over-year comparisons are significantly affected by our acquisitions, dispositions and construction of towers. Our acquisition of MIPT, which closed onin October 1, 2013, significantly impacts the comparability of reported results between periods. Our principal acquisitions are described in note 6 to our consolidated financial statements included in this Annual Report.

ITEM 7.

MANAGEMENT’S DISCUSSION AND ANALYSIS OF FINANCIAL CONDITION AND RESULTS OF OPERATIONS

The discussion and analysis of our financial condition and results of operations that follow are based upon our consolidated financial statements, which have been prepared in accordance with GAAP. The preparation of our financial statements requires us to make estimates and judgments that affect the reported amounts of assets and liabilities, revenues and expenses and the related disclosure of contingent assets and liabilities at the date of our financial statements. Actual results may differ significantly from these estimates under different assumptions or conditions. This discussion should be read in conjunction with our consolidated financial statements hereinincluded in this Annual Report and the accompanying notes, thereto, and the information set forth under the caption “Critical Accounting Policies and Estimates” below.

Our continuing operations are reported in three segments,segments: domestic rental and management, international rental and management and network development services. AmongIn evaluating operating performance in each business segment, management uses, among other factors, management uses segment gross margin and segment operating profit in its assessment of operating performance in each business segment.profit. We define segment gross margin as segment revenue less segment operating expenses, excluding stock-based compensation expense recorded in costs of operations; Depreciation, amortization and accretion; Selling, general, administrative and development expense; and Other operating expense. We define segment operating profit as segment gross margin less Selling, general, administrative and development expense attributable to the segment, excluding stock-based compensation expense and corporate expenses. Segment gross margin and segment operating profit for the international rental and management segment also include Interest income, TV Azteca, net (see note 21 to our consolidated financial statements included herein)in this Annual Report). These measures of segment gross margin and segment operating profit are also before Interest income, Interest expense, LossGain (loss) on retirement of long-term obligations, Other income (expense), Net income (loss) attributable to noncontrolling interest, Income (loss) on equity method investments and Income tax provision (benefit)benefit (provision).

Executive Overview

We are a global independent owner, operator and developer of communications real estate. Our primary business is the leasing antennaof space on multi-tenant communications sites to wireless service providers, radio and television broadcast companies, wireless data and data providers, government agencies and municipalities and tenants in a number of other industries. In addition to the communications sites in our portfolio, we manage rooftop and tower sites for property owners under various contractual arrangements. We also hold property interests that we lease to communications service providers and third-party tower operators. We refer to this business as our rental and management operations, which accounted for approximately 98% of our total revenues for the year ended December 31, 20132014 and includes our domestic rental and management segment and our international rental and management segment. Through our network development services, we offer tower-related services domestically, including site acquisition, zoning and permitting services and structural analysis services, which primarily support our site leasing business and the addition of new tenants and equipment on our sites.sites, including in connection with provider network upgrades. We began operatingoperate as a REIT for U.S. federal income tax purposes effective January 1, 2012.purposes.

The following table details the number of communications sites, excluding managed sites, we owned or operated as of December 31, 2013:2014:

On February 5, 2015, we signed a definitive agreement for the Proposed Verizon Transaction, pursuant to which we expect to acquire the exclusive right to lease, acquire or otherwise operate and manage up to 11,489 wireless communications sites in the United States for $5.056 billion in cash at closing, subject to certain conditions and limited adjustments.

The majority of our tenant leases with wireless carriers have an initial non-cancellable term of five to ten years, with multiple five-year renewal terms. Accordingly, nearly all of the revenue generated by our rental and management operations during the year ended December 31, 20132014 was recurring revenue that we should continue to receive in future periods. Based upon foreign currency exchange rates and the tenant leases in place as of December 31, 2013,2014, we expect to generate approximately $23$27 billion of non-cancellable tenant lease revenue over future periods, absent the impact of straight-line lease accounting. Most of our tenant leases have provisions that periodically increase the rent due under the lease, typically annually based on a fixed escalation (approximately 3.0%-3.5% in the United States) or an inflationary index in our international markets.markets, or a combination of both. In addition, certain of our tenant leases provide for additional revenue to cover costs, such as ground rent or power and fuel costs.

The revenues generated by our rental and management operations may also be affected by cancellations of existing tenant leases. As discussed above, most of our tenant leases with wireless carriers and broadcasters are multi-year contracts, which typically are non-cancellable; however in some instances, a lease may be canceled upon the payment of a termination fee.

Revenue lost from either cancellations of leases at the end of their terms or rent negotiations historically havehas not had a material adverse effect on the revenues generated by our rental and management operations. During the year ended December 31, 2013,2014, loss of annual revenue from tenant lease cancellations or renegotiations represented less thanapproximately 1.5% of our rental and management operations revenues.

Rental and Management Operations Revenue Growth. OurDue to our diversified communications site portfolio, our tenant lease rates vary considerably depending upon numerous factors, including, but not limited to, amount and type of tenant equipment on the tower, ground space required by the tenant, remaining tower capacity and

tower location. We measure the remaining tower capacity by assessing several factors, including tower height, tower type, environmental conditions, existing equipment on the tower and zoning and permitting regulations in effect in the jurisdiction where the tower is located. In many instances, tower capacity can be increased through tower augmentation.

The primary factors affecting the revenue growth in our domestic and international rental and management revenue growth is comprised of (i) growth insegments are: