We areMarkel Corporation is a diverse financial holding company serving a variety of niche markets. Our principal business markets and underwrites specialty insurance products. We believe that our specialty product focus and niche market strategy enable us to develop expertise and specialized market knowledge. We seek to differentiate ourselves from competitors by our expertise, service, continuity and other value-based considerations. We also own interests in various businesses that operate outside of the specialty insurance marketplace. Our financial goals are to earn consistent underwriting and operating profits and superior investment returns to build shareholder value.

Our business is comprised of the following types of operations:

The specialty insurance market differs significantly from the standard market. In the standard market, insurance rates and forms are highly regulated, products and coverages are largely uniform with relatively predictable exposures and companies tend to compete for customers on the basis of price. In contrast, the specialty market provides coverage for hard-to-place risks that generally do not fit the underwriting criteria of standard carriers.

Competition in the specialty insurance market tends to focus less on price than in the standard insurance market and more on other value-based considerations, such as availability, service and expertise. While specialty market exposures may have higher perceived insurance risks than their standard market counterparts, we seek to manage these risks to achieve higher financial returns. To reach our financial and operational goals, we must have extensive knowledge and expertise in our chosen markets. Many of our larger accounts are considered on an individual basis where customized forms and tailored solutions are employed.

By focusing on the distinctive risk characteristics of our insureds, we have been able to identify a variety of niche markets where we can add value with our specialty product offerings. Examples of niche insurance markets that we have targeted include wind and earthquake-exposed commercial properties, liability coverage for highly specialized professionals, equine-related risks, workers' compensation insurance for small businesses, classic cars, credit and surety-related risks, lender services and marine, energy and environmental-related activities. Our market strategy in each of these areas of specialization is tailored to the unique nature of the loss exposure, coverage and services required by insureds. In each of our niche markets, we assign teams of experienced underwriters and claims specialists who provide a full range of insurance services.

Our E&S insurance operations are conducted through Evanston Insurance Company (Evanston), an Illinois domiciled in Illinois.insurance company. The majority of our specialty admitted insurance operations are conducted through Markel Insurance Company (MIC), domiciled in Illinois; Markel American Insurance Company (MAIC), domiciled in Virginia; FirstComp Insurance Company (FCIC), domiciled in NebraskaNebraska; and Essentia Insurance Company (Essentia), domiciled in Missouri. Beginning in 2017, ourOur specialty admitted operations also include Suretec Insurance Company (SIC), Suretec Indemnity Company (SINC), State National Insurance Company, Inc. (SNIC) and National Specialty Insurance Company (NSIC), all of which are domiciled in Texas.Texas, and Suretec Indemnity Company (SINC), which is domiciled in California. Our United StatesU.S. reinsurance operations are conducted through Markel Global Reinsurance Company (Markel Global Re), a Delaware-domiciled reinsurance company.

In 2017, 21%2019, 19% of gross premium writings from our underwriting segmentsoperations related to foreign risks (i.e., coverage for risks or cedents located outside of the United States)U.S.), of which 34%36% were from the United KingdomU.K. and 12% were from Canada. In 2016, 23% of our premium writings related to foreign risks, of which 32%There were from the United Kingdom and 11% were from Canada. In 2015, 24% of our premium writings related to foreign risks, of which 37% were from the United Kingdom and 10% were from Canada. In each of these years, there was no other individual foreign countrycountries from which premium writings were material. Premium writings are attributed to individual countries based upon location of risk or cedent. See note 8(d) of the notes to consolidated financial statements for additional information.

Most of our business is placed through insurance and reinsurance brokers.brokers and retail insurance agents. Some of our insurance business is also placed through managing general agents.agents, third parties who have been granted authority to bind risks on our behalf in accordance with underwriting guidelines we prescribe. We seek to develop and capitalize on relationships with insurance and reinsurance brokers, insurance and reinsurance companies, large global corporations and financial intermediaries to develop and underwrite business. A significant volume of premium for the property and casualty insurance and reinsurance industry is produced through a small number of large insurance and reinsurance brokers. During the years ended December 31, 2017, 2016 and 2015,In 2019, the top three independent brokers accounted for 27%, 28% and 27%, respectively, of gross premiums written in our underwriting segments. See note 8(d) of the notes to consolidated financial statements for additional information. Additionally, a significant portion of the reinsurance contracts securitized through our insurance-linked securities operations, for the benefit of third party investors, are placed through these top three independent brokers.

We compete with numerous domestic and international insurance companies and reinsurers, Lloyd's syndicates, risk retention groups, insurance buying groups, risk securitization programs, alternative capital sources and alternative self-insurance mechanisms. We also compete with new companies that continue to be formed to enter the insurance and reinsurance markets, particularly companies with new or "disruptive" technologies or business models. Competition may take the form of lower prices, broader coverages, greater product flexibility, higher coverage limits, higher quality services or higher ratings by independent rating agencies. In all of our markets, we compete on the basis of overall financial strength, ratings assigned by developingindependent rating agencies, development of specialty products to satisfy well-defined market needs and by maintaining relationships with agents, brokers and insureds who rely on our expertise. This expertise is our principal means of competing. We offer a diverse portfolio of products, each with its own distinct competitive environment, which enablesrequires us to be responsive to changes in market conditions for individual product lines. With each of our products, we seek to competewrite business that produces underwriting profits by competing with innovative ideas, appropriate pricing, expense control and quality service to policyholders, agents and brokers.

Few barriers exist to prevent insurers and reinsurers from entering our markets ofwithin the property and casualty industry. Market conditions and capital capacity influence the degree of competition at any point in time. PeriodsDuring periods of intense competition, which typically include broader coverage terms, lower prices and excess underwriting capacity, are referred to as a "soft market." A favorable insurance market is commonly referred to as a "hard market" and is characterizeddefined by stricter coverage terms, higher prices and lower underwriting capacity. During soft markets, unfavorable conditions exist due in part to what many perceive as excessive amountsavailability of capital, competition can result in the industry. In an attempt to use their capital, many insurance companies seek to write additional premiums without appropriate regardlower pricing and less favorable policy terms and conditions for ultimate profitability,insurers. During periods of reduced underwriting capacity, pricing and standard insurance companiespolicy terms and conditions are generally more willing to write specialty coverages. The opposite is typically true during hard markets.favorable for insurers. Historically, the performance of the property and casualty reinsurance and insurance industries has tended to fluctuate in cyclical periods of price competition and excess underwriting capacity, followed by periods of high premium rates and shortages of underwriting capacity. At any given time, our portfolio of insurance products could be experiencing varying combinations of these characteristics. This cyclical market pattern can be more pronounced in the specialty insurance and reinsurance markets in which we compete than the standard insurance market.

We routinely review the pricing of our major product lines and will continue to pursue price increases in 2018,2020, when possible. However, when we believe the prevailing market price will not support our underwriting profit targets, the business is not written. As a result of our underwriting discipline, gross premium volume may vary when we alter our product offerings to maintain or improve underwriting profitability.

By focusing on market niches where we have underwriting expertise, we seek to earn consistent underwriting profits, which are a key component of our strategy. The property and casualty insurance industry commonly defines underwriting profit or loss as earned premiums net of losses and loss adjustment expenses and underwriting, acquisition and insurance expenses. We believe that the ability to achieve consistent underwriting profits demonstrates knowledge and expertise, commitment to superior customer service and the ability to manage insurance risk. We use underwriting profit or loss as a basis for evaluating our underwriting performance. To facilitate this strategy, we have a product line leadership group that has primary responsibility for both developing and maintaining underwriting and pricing guidelines on our existing products and new product development. The product line leadership group is under the direction of our Chief Underwriting Officer.

See note 208 of the notes to consolidated financial statements for additional segment reporting disclosures.

Our Insurance segment reported gross premium volume of $5.3 billion, earned premiums of $4.1 billion and Global Insurance divisions were combined to form the an underwriting profit of $309.8 million in 2019.

The Markel Specialty division writes program insurance and other specialty coverages for well-defined niche markets, primarily on an admitted basis. Our business written in the admitted market focuses on risks that, although unique and hard-to-place in the standard market, must remain with an admitted insurance company for marketing and regulatory reasons. Hard-to-place risks written in the admitted market cover insureds engaged in similar, but highly specialized, activities that require a total insurance program not otherwise available from standard insurers or insurance products that are overlooked by large admitted carriers. The admitted market is subject to more state regulation than the E&S market, particularly with regard to rate and form filing requirements, restrictions on the ability to exit lines of business, premium tax payments and membership in various state associations, such as state guaranty funds and assigned risk plans.

The majority of our businessBusiness written in the Markel Specialty division is primarily written by retail insurance agents who have very limited or no underwriting authority although weauthority. We also utilize managing general agents, who have broader underwriting authority, for certain of our product lines. Agents are carefully selected and agency business is controlled through regular audits and pre-approvals. Certain products and programs are marketed directly to consumers or distributed through wholesale producers. Personal lines coverages included in this segment are marketed directly to the consumer using direct mail, internet and telephone promotions, as well as relationships with various motorcycle and boat manufacturers, dealers and associations.

The majority of the business produced by this division is written either through MIC, MAIC, FCIC, Essentia SIC, and SINC.MAIC. MIC MAIC and Essentia, which specializes in coverage for classic cars and boats, are licensed to write property and casualty insurance in all 50 states and the District of Columbia. MAIC is also licensed to write property and casualty insurance in Puerto Rico. Essentia specializes in coverage for classic cars and boats. FCIC is currently licensed in 28 states and specializes in workers' compensation coverage. SIC and SINC specialize in surety coverages. SIC is currently licensed in all 50 states and the District of Columbia. SINC is currently licensed in California and Texas.

The State National division writes collateral protection insurance, (CPI), which insures personal automobiles and other vehicles held as collateral for loans made by credit unions, banks and specialty finance companies through its lender services product line on both an admitted and non-admitted basis. This business is primarily written on SNIC and NSIC, which are licensed to write property and casualty insurance in all 50 states and the District of Columbia.

General Liability product offerings include a variety of primary and excess liability coverages targeting apartments and office buildings, retail stores, contractors, consultants, construction professionals, financial service professionals, professional practices, social welfare organizations and contractors,medical products, as well as businessbusinesses in the life sciences, energy, medical, healthcare, pharmaceutical, recreational, transportation, heavy industrial and hospitality industries. Specific products include the following:

Professional liability coverages include unique solutions for highly specialized professions, including architects and engineers, lawyers, accountants, agents and brokers, service technicians and computer consultants. We offer claims-made medical malpractice coverage for doctors and dentists; claims-made professional liability coverage to individual healthcare providers such as therapists, pharmacists, physician assistants and nurse anesthetists; and coverages for medical facilities and other allied healthcare risks such as clinics, laboratories, medical spas, home health agencies, small hospitals, pharmacies and senior living facilities. Other professional liability coverages include errors and omissions, union liability, professional indemnity, intellectual property, executive liability for financial institutions and Fortune 1000 companies and management liability. Our management liability coverages, which can be bundled with other coverages or written on a standalone basis, include employment practices liability, directors' and officers' liability and fiduciary liability coverages. Additionally, we offer cyber liability products, which provide coverage primarily for data breach and privacy liability, data breach loss to insureds and electronic media coverage.

Personal lines products provide first and third party coverages for classic cars, motorcycles and a variety of personal watercraft, including vintage boats, high performance boats and yachts and recreational vehicles, such as motorcycles, snowmobiles and ATVs. Based on the seasonal nature of much of our personal lines business, we generally will experience higher claims activity during the second and third quarters of the year. Additionally, property coverages are offered for mobile homes, dwellings and homeowners that do not qualify for standard homeowner's coverage. Other products offered include special event protection performance bicycle coverage,and pet health coverage, supplemental natural disaster coverage, renters' protection coveragecoverage.

Property coverages consist principally of fire, allied lines (including windstorm, hail and water damage) and other specialized property coverages, including catastrophe-exposed property risks such as earthquake and wind on both a primary and excess flood coverage.basis. Catastrophe-exposed property risks are typically lower frequency and higher severity in nature than more standard property risks. Our property coverages are exposed to windstorm losses that, based on the seasonal nature of those events, are more likely to occur in the third and fourth quarters of the year. Our property risks range from small, single-location accounts to large, multi-state, multi-location, multi-national accounts on a worldwide basis. Other types of property products include inland marine products, railroad-related products and specie coverage for fine art on exhibition and in private collections.

Specialty programs business included in this segment is offered on a standalone or package basis and generally targets specialized commercial markets and customer groups. Targeted groups include youth and recreation oriented organizations and camps, child care operators, schools, social service organizations, museums and historic homes, performing arts organizations, senior living facilities and wineries. Other specialty programs business written in this segment includes:

Other product lines within the U.S. Insurance segment include:

Our Reinsurance segment includes property, casualty and casualtyspecialty treaty reinsurance products offered to other insurance and reinsurance companies globally through the broker market. Our treaty reinsurance offerings include both quota share and excess of loss reinsurance and are typically written on a participation basis, which means each reinsurer shares proportionally in the business ceded under the reinsurance treaty written. Our reinsurance products may include features such as contractual provisions that require our cedent to share in a portion of losses resulting from ceded risks, may require payment of additional premium amounts if we incur greater losses than those projected at the time of the execution of the contract, may require reinstatement premium to restore the coverage after there has been a loss occurrence or may provide for experience refunds if the losses we incur are less than those projected at the time the contract is executed. OurSubstantially all of our reinsurance product offerings are underwritten by our Global Reinsurance division and our Markel International division. The Global Reinsurance division operates from platforms in the United StatesU.S., Bermuda and Bermuda.the U.K. Business written in the Global Reinsurance division is produced primarily through Markel Global Re, and Markel Bermuda. Markel Global Rewhich is licensed or accredited to provide reinsurance in all 50 states and the District of Columbia. The Global Reinsurance division also writes business through Markel Bermuda conducts its reinsurance operations from Bermuda. Theand Markel International division conducts its reinsurance operations from its London-based platform, as described above, and from its platform in Latin America, which includes Markel Brazil.Syndicate 3000.

Our casualty treaty reinsurance programs are written on a quota share and excess of loss basis and include general liability, professional liability, medical malpractice and environmental impairment liability. General liability reinsurance includes umbrella and excess casualty products that are written worldwide. Our professional liability reinsurance programs are offered worldwide and consist of directors and officers liability, including publicly traded, private, and non-profit companies in both commercial and financial institution arenas; lawyers errors and omissions for small, medium and large-sized law firms; accountants errors and omissions for small and medium-sized firms; technology errors and omissions and cyber liability focusing on network security and privacy exposures. Medical malpractice reinsurance products are offered in the United States and include coverage for physician, surgeon, hospital and long term care medical malpractice writers. Environmental treaty reinsurance provides coverage for pollution legal liability, contractors pollution and professional liability exposures on both a nationwide and regional basis within the U.S.

Specialty treaty reinsurance products offered in the Reinsurance segment fall withininclude structured and whole turnover credit, political risk, mortgage and contract and commercial surety reinsurance programs covering worldwide exposures, public entity reinsurance products, workers' compensation excess of loss and quota share treaties, whole account, marine and agriculture reinsurance products. Our mortgage products offer coverage for private mortgage insurers in the following major product groupings:U.S., Australia and Europe. Our public entity reinsurance products offer customized programs for government risk pools, including counties, municipalities, schools, public housing authorities and special districts (e.g., water, sewer, parks) located in the U.S. Types of coverage for public entities include general liability, environmental impairment liability, cyber and errors and omissions. Our workers' compensation business includes standard and catastrophe exposed workers' compensation business. Marine reinsurance products include offshore and onshore marine and energy risks on a worldwide basis, including hull, cargo and liability. Agriculture reinsurance covers multi-peril crop insurance, hail and related exposures, for risks located in the U.S. and Canada.

Property treaty products are offered on an excess of loss and quota share basis for catastrophe, per risk and retrocessional exposures worldwide. Our catastrophe exposures are generally written on an excess of loss basis and target both personal and commercial lines of business providing coverage for losses from natural disasters, including hurricanes, wind storms and earthquakes. We also reinsure individual property risks such as buildings, structures, equipment and contents and provide coverage for both personal lines and commercial property exposures. Our retrocessional products provide coverage for all types of underlying exposures and geographic zones. A significant portion of the property treaty business covers United StatesU.S. exposures, with the remainder coming from international property exposures.

Within our underwriting operations, we purchase reinsurance and retrocessional reinsurance to manage our net retention on individual risks and overall exposure to losses, while providing us with the ability to offer policies with sufficient limits to meet policyholder needs. See "Program Services" section below for an overview of ceded reinsurance within our program services business, which is managed separately from our underwriting operations.

In a reinsurance and retrocession transactions,transaction, an insurance or reinsurance company transfers, or cedes, all or part of its exposure in return for a portion of the premium. In a retrocessional reinsurance transaction, a reinsured exposure is further ceded to another reinsurer. We purchase catastrophereinsurance and retrocessional reinsurance coverage for our catastrophe-exposed policies to ensure that our net retained catastrophe risk is within our corporate tolerances. Beginning in late 2018, we shifted from buying proportional catastrophe reinsurance or retrocessional reinsurance coverages towards excess of loss catastrophe coverages in both our Insurance and Reinsurance segments. On other product lines for which we purchase reinsurance or retrocessional reinsurance, we are also beginning to shift from purchasing coverages related to specific lines of business towards enterprise-wide coverages. Both of these changes allow us to retain more of our profitable business while continuing to manage volatility within our underwriting results. As a result of these changes, we are retaining more gross premium volume and have lower ceding commissions within our underwriting segments. Net retention of gross premium volume in our underwriting segments was 84% in 20172019 and 83% in 2016. We do not purchase or sell finite reinsurance products or use other structures that would have the effect of discounting loss reserves.2018.

Our ceded reinsurance and retrocessional contracts do not legally discharge us from our primary liability for the full amount of the policies, and we will be required to pay the loss and bear collection risk if the reinsurer fails to meet its obligations under the reinsurance agreement. We attempt to minimize credit exposure to reinsurers through adherence to internal ceded reinsurance guidelines. We manage our exposures so that no exposure to any one reinsurer is material to our ongoing business. To participate in our reinsurance program, prospective companies generally must: (i) maintain an A.M. Best Company (Best) or Standard & Poor's (S&P) rating of "A" (excellent) or better; (ii) maintain minimum capital and surplus of $500 million and (iii) provide collateral for recoverables in excess of an individually established amount. In addition, certain foreign reinsurers for our United StatesU.S. insurance operations must provide collateral equal to 100% of recoverables, with the exception of reinsurers who have been granted certified or authorized status by an insurance company's state of domicile. Our credit exposure to Lloyd's syndicates is managed through individual and aggregate exposure thresholds.

When appropriate, we pursue reinsurance commutations that involve the termination of ceded reinsurance and retrocessional reinsurance contracts. Our commutation strategy related to ceded reinsurance and retrocessional contracts is to reduce credit exposure and eliminate administrative expenses associated with the run-off of ceded reinsurance placed with certain reinsurers.

The following table displays balances recoverable from our ten largest reinsurers by group from our underwriting operations at December 31, 2017.2019. The contractual obligations under reinsurance and retrocessional contracts are typically with individual subsidiaries of the group or syndicates at Lloyd's and are not typically guaranteed by other group members or syndicates at Lloyd's. These ten reinsurance groups represent approximately 61% of our $2.6 billion reinsurance recoverable balance attributed to our underwriting operations, before considering allowances for bad debts.

Reinsurance and retrocessional treaties are generally purchased on an annual or biennial basis and are subject to renegotiations at renewal. In most circumstances, the reinsurer remains responsible for all business produced before termination. Treaties typically contain provisions concerning ceding commissions, required reports to reinsurers, responsibility for taxes, arbitration in the event of a dispute and provisions that allow us to demand that a reinsurer post letters of credit or assets as security if a reinsurer becomes an unauthorized reinsurer under applicable regulations or if its rating falls below an acceptable level.

See note 1511 of the notes to consolidated financial statements and Management's Discussion & Analysis of Financial Condition and Results of Operations for additional information about our ceded reinsurance programs and exposures.

Our business strategy recognizes the importance of both consistent underwriting and operating profits and superior investment returns to build shareholder value. We rely on sound underwriting practices to produce investable funds while minimizing underwriting risk. The majority of our investable assets come from premiums paid by policyholders. Policyholder funds are invested predominantly in high-quality corporate, government, municipal and municipalcorporate bonds that generally match the duration and currency of our loss reserves. The balance, comprised of shareholder funds, is available to be invested in equity securities, which over the long run, have produced higher returns relative to fixed maturity investments. When purchasing equity securities, we seek to invest in profitable companies, with honest and talented management, that exhibit reinvestment opportunities and capital discipline, at reasonable prices. We intend to hold these investments over the long term. Substantially all of our investment portfolio is managed by company employees.

We evaluate our investment performance by analyzing net investment income and net realizedinvestment gains (losses) as well as our taxable equivalent total investment return, which is a non-GAAP financial measure. Taxable equivalent total investment return includes items that impact net income, such as coupon interest on fixed maturities, dividends on equity securities and realized investment gains or losses, as well as changes in unrealized gains or losses on available-for-sale securities, which do not impact net income. Certain items that are included in net investment income have been excluded from the calculation of taxable equivalent total investment return, such as amortization and accretion of premiums and discounts on our fixed maturity portfolio, to provide a comparable basis for measuring our investment return against industry investment returns. The calculation of taxable equivalent total investment return also includes the current tax benefit associated with income on certain investments that is either taxed at a lower rate than the statutory income tax rate or is not fully included in federalU.S. taxable income. We believe the taxable equivalent total investment return is a better reflection of the economics of our decision to invest in certain asset classes. We do not lower the quality of our investment portfolio in order to enhance or maintain yields. We focus on long-term total investment return, understanding that the level of realized and unrealized investment gains or losses and unrealized gains or losses on available-for-sale securities may vary from one period to the next.

The following table summarizes our investment performance.

We believe our investment performance is best analyzed from the review of taxable equivalent total investment return over several years. The following table presents taxable equivalent total investment return before and after the effects of foreign currency movements.

The following table reconciles investment yield to taxable equivalent total investment return.

We monitor our investment portfolio to ensure that credit risk does not exceed prudent levels. S&P and Moody's provide corporate and municipal debt ratings based on their assessments of the credit quality of an obligor with respect to a specific obligation. S&P's ratings range from "AAA" (capacity to pay interest and repay principal is extremely strong) to "D" (debt is in payment default). Securities with ratings of "BBB" or higher are referred to as investment grade securities. Debt rated "BB" and below is regarded by S&P as having predominantly speculative characteristics with respect to capacity to pay interest and repay principal. Moody's ratings range from "Aaa" to "C" with ratings of "Baa" or higher considered investment grade.

Our fixed maturity portfolio has an average rating of "AA," with 98% rated "A" or better by at least one nationally recognized rating organization. Our policy is to invest in investment grade securities and to minimize investments in fixed maturities that are unrated or rated below investment grade. At December 31, 2017,2019, less than 1% of our fixed maturity portfolio was unrated or rated below investment grade. Our fixed maturity portfolio includes securities issued with financial guaranty insurance. We purchase fixed maturities based on our assessment of the credit quality of the underlying assets without regard to insurance.

The following chart presents our fixed maturity portfolio, at estimated fair value, by rating category at December 31, 2017.2019.

See "Market Risk Disclosures" in Management's Discussion & Analysis of Financial Condition and Results of Operations for additional information about investments.

In July 2019, MCIM announced it would cease accepting new investments in the Markel CATCo Funds and would not write any new business in Markel CATCo Re. Both the Markel CATCo Funds and Markel CATCo Re have been placed into run-off, returning capital to investors as it becomes available. For further details regarding developments within our Markel CATCo operations, see note 20 of the investment funds that it manages. Total revenues attributednotes to MCIM for the year ended December 31, 2017 were $28.7 million. consolidated financial statements.

In 2019, we established Lodgepine Capital Management Limited (Lodgepine), our new retrocessional insurance-linked securities fund manager in Bermuda. Lodgepine's initial product offering will be Lodgepine Fund Limited, a property catastrophe retrocessional investment fund, which is expected to launch in 2020. We have committed to invest up to $100 million in Lodgepine Fund Limited. Lodgepine Fund Limited initially plans to subscribe to a portfolio of retrocessional reinsurance, which includes $6.0 billion for unconsolidated variable interest entities.contracts written in our Reinsurance segment.

Through our wholly owned subsidiary Markel Ventures, Inc. (Markel Ventures), we own interests in various businesses that operate outside of the specialty insurance marketplace. These businesses are viewed by management as separate and distinct from our insurance operations. Local management teams oversee the day-to-day operations of these companies, while strategic decisions, including investment and capital allocation decisions, are made in conjunction with members ofby our executivesenior management team.

Our strategy in making these investments is similar to our strategy for purchasing equity securities. We seek to invest in profitable companies, with honest and talented management, that exhibit reinvestment opportunities and capital discipline, at reasonable prices. We intend to own the businesses acquired for a long period of time.

Our chief operating decision maker allocates resources to and assesses the performance of these various businesses in the aggregate as the Markel Ventures operations are comprised ofsegment. This segment includes a diverse portfolio of businesses. While eachbusinesses from different industries that offer various types of products and services to businesses and consumers. See note 8 of the businesses is operated independently from one another, we aggregate theirnotes to consolidated financial results into two industry groups: manufacturing and non-manufacturing. Our manufacturing operations are comprised of manufacturers of transportation and other industrial equipment. Our non-manufacturing operations are comprised of businesses from several industry groups, including consumer goods and services (including healthcare) and business services.statements for additional segment reporting disclosures.

We historically monitored and assessedDuring the performance of each of our Markel Ventures businesses separately with no single business being individually significant to the operations of the Company as a whole. Following the continued growth inlast three years, our Markel Ventures operations have expanded through acquisitions of majority interests in various businesses, including the Costa Farms companies, Brahmin Leather Works, LLC and its aggregate significanceVSC Fire & Security, Inc. See note 2 of the notes to ourconsolidated financial results, beginning in 2018, we will monitor and report our Markel Ventures operations as a single operating segment, consistent with the way our chief operating decision maker now reviews and assesses Markel Ventures’ performance.statements for additional details related to these acquisitions.

In July 2019, MCIM announced it would cease accepting new investments in the Markel CATCo Funds and would not write any new business in Markel CATCo Re. Both the Markel CATCo Funds and Markel CATCo Re have been placed into run-off, returning capital to investors as it becomes available. For further details regarding developments within our Markel VenturesCATCo operations, see note 20 of the notes to consolidated financial statements.

Our financial goals are to earn consistent underwriting and operating profits and superior investment returns to build shareholder value. More specifically, weWe measure financial success by our ability to grow book value per share and the market price per share of our stock, or total shareholder return, at a high raterates of return over a long period of time. To mitigate the effects of short-term volatility, we generally use five-year time periods to measure ourselves. Growth in book value per share is an important measure of our success because it includes all underwriting, operating and investing results. For the year ended December 31, 2017,2019, book value per share increased 13% primarily due to a $763.0 million increase in net unrealized gains on investments, net of taxes, and net income to shareholders of $395.3 million. For the year ended December 31, 2016, book value per share increased 8%23% primarily due to net income to shareholders of $455.7 million$1.8 billion and a $242.2$298.0 million increase in net unrealized gains on investments, net of taxes. Over the past five years, we have grown book value per share at a compound annual rate of 11%8% to $683.55 per share. As we continue to expand our operations beyond underwriting and investing, we recognize that book value$802.59 per share does not capture allat December 31, 2019. Growth in total shareholder value is also an important measure of the economic value in our business,success, as a growingsignificant portion of our operations are not recorded at fair value or otherwise captured in book value. As a result, beginning in 2018, we will also measure our financial success through the growth in the market price of a share of our stock, or total shareholder return, over a long period of time. For the year ended December 31, 2017,2019, our stock price per share price increased 26%10%. Over the past five years, our stock price per share price increased at a compound annual rate of 21%11%.

The following graph presents book value per share and stock price per share price for the past five years as of December 31.

The following is a summary of significant regulations that apply to our businesses, alsobut it is not intended to be a comprehensive review of every regulation to which we are subjectsubject. For information regarding risks associated with regulations applicable to regulation and supervision by regulatory authorities of the various jurisdictions in which they conduct business.us, see “Item 1A - Risk Factors.”

Financial stability and strength are important purchase considerations of policyholders, cedents and insurance agents and brokers. Because an insurance premium paid today purchases coverage for losses that might not be paid for many years, the financial viability of the insurer is of critical concern. Various independent rating agencies provide information and assign ratings to assist buyers in their search for financially sound insurers. Rating agencies periodically re-evaluate assigned ratings based upon changes in the insurer's operating results, financial condition or other significant factors influencing the insurer's business. Changes in assigned ratings could have an adverse impact on an insurer's ability to write new business.

Best assigns financial strength ratings (FSRs) to property and casualty insurance companies based on quantitative criteria such as profitability, leverage and liquidity, as well as qualitative assessments such as the spread of risk, the adequacy and soundness of ceded reinsurance, the quality and estimated market value of assets, the adequacy of loss reserves and surplus and the competence, experience and integrity of management. Best's FSRs range from "A++" (superior) to "F" (in liquidation).

SeventeenEighteen of our nineteen insurance subsidiaries are rated by Best. All seventeeneighteen of our insurance subsidiaries rated by Best have been assigned an FSR of "A" or "A-" (excellent). Our Lloyd's syndicate is part of a group rating for the Lloyd's overall market, which has been assigned an FSR of "A" (excellent) by Best.

Nine of our nineteen insurance subsidiaries are rated by S&P. All nine of our insurance subsidiaries rated by S&P have been assigned an FSR of "A" (strong). Our Lloyd's syndicate is part of a group rating for the Lloyd's overall market, which has been assigned an FSR of "A+" (strong) by S&P.

Five of our nineteen insurance subsidiaries are rated by Moody's Corporation (Moody's). All five insurance subsidiaries rated by Moody's have been assigned an FSR of "A2" (good).

A wide range of factors could materially affect our future prospects and performance. The matters addressed under "Safe Harbor and Cautionary Statement," "Critical Accounting Estimates" and "Market Risk Disclosures" in Management's Discussion and Analysis of Financial Condition and Results of Operations and other information included or incorporated in this report describe many of the significant risks that could affect our operations and financial results. We are also subject to the following risks.

This process assumes that past experience, adjusted for the effects of current developments and anticipated trends, is an appropriate basis for predicting future events. There is no precise method, however, for evaluating the impact of any specific factor on the adequacy of reserves, and actual results will differ from original estimates. As part of the reserving process, we regularly review our loss reserves and make adjustments as necessary. Future increases in loss reserves for our underwriting operations will, and for our programs services operations may, result in additional charges to earnings, which may be material.

In addition, reinsurance reserves are subject to greater uncertainty than insurance reserves primarily because a reinsurer relies on (i) the original underwriting decisions and claims decisions made by ceding companies and (ii) information and data from ceding companies. As a result, we are subject to the risk that our ceding companies may not have adequately evaluated the risks reinsured by us and the premiums ceded may not adequately compensate us for the risks we assume. In addition, reinsurance reserves may be less reliable than insurance reserves because there is generally a longer lapse of time from the occurrence of the event to the reporting of the loss or benefit to the reinsurer and ultimate resolution or settlement of the loss.

We expect mortality, morbidity, longevity, and lapse experience to fluctuate somewhat from period to period, but believe they should remain reasonably predictable over a period of many years. Mortality, longevity, morbidity or lapse experience that is less favorable than the mortality, longevity, morbidity or lapse rates that we used in establishing the reserves for a reinsurance agreement will negatively affect our net income because the reserves we originally set for the risks we assumed may not be sufficient to cover the future claims and expense payments. Furthermore, even if the total benefits paid over the life of the contract do not exceed the expected amount, unexpected increases in the incidence of deaths or illness can cause usresult in changes to pay more benefitsour assumptions in a given reporting period, than expected, adversely affecting our net income in any particular reporting period. Fluctuations in interest rates will impact the performance of our investments.investments related to our life and annuity reinsurance book. If there are changes to any of the above factors to the point where a reserve deficiency exists, a charge to earnings will be recorded, which may have a material adverse impacteffect on our results of operations and financial condition.

The ceding of insurance does not legally discharge us from our primary liability for the full amount of the policies. Reliance on reinsurance recoveries may create credit risk as a result of the reinsurer's inability or unwillingness to pay reinsurance claims when due. We generally select well capitalized and highly rated reinsurers and in certain instances we require reinsurers to post substantial collateral to secure the reinsured risks. Deterioration in the credit quality of existing reinsurers or disputes over the terms of reinsurance could result in charges to earnings, which may have a material adverse impacteffect on our results of operations and financial condition. In addition, collateral may not be sufficient to cover our liability,the reinsurer’s obligation to us, and we may not be able to cause the reinsurer to deliver additional collateral.

As of December 31, 2017,2019, we were the beneficiary of letters of credit, trust accounts and funds withheld in the aggregate amount of $2.7$2.9 billion, collateralizing $4.7$5.4 billion in reinsurance recoverables. The remaining unsecured reinsurance recoverables are ceded to highly-rated, well capitalized reinsurers. Our reinsurance recoverables are based on estimates, and our actual liabilities may exceed the amount we are able to recover from our reinsurers or any collateral securing the liabilities. The failure of a reinsurer to meet its obligations to us, whether due to insolvency, dispute or other unwillingness or inability to pay, or due to our inability to access sufficient collateral to cover our liabilities, could have a material adverse effect on our results of operations and financial condition.

The availability and cost of reinsurance are determined by market conditions beyond our control. There is no guarantee that our desired amounts of reinsurance or retrocessional reinsurance will be available in the marketplace in the future. In addition, available capacity may not be on terms we deem appropriate or acceptable or with companies with whom we want to do business. This could have a material adverse effect on our results of operations and financial condition.

In addition, we are subject to numerous data privacy laws and regulations enacted in the jurisdictions in which we do business. A misuse or mishandling of confidential or proprietary information being sent to or received from a client, employee or third party could damage our businesses or our reputation or result in significant monetary damages, regulatory enforcement actions, fines and criminal prosecution in one or more jurisdictions. For example, under the European General Data Protection Regulation there are significant new punishments for non-compliance which could result in a penalty of up to 4% of a firm’s global annual revenue. In addition, a violation of data privacy laws and regulations could result in defaults under our outstanding indebtedness or credit facilities. Those monetary damages, penalties, regulatory or legal actions or defaults, or the damage to our businesses or reputation, could have a material adverse effect on our results of operations and financial condition. Third parties to whom we outsource certain functions are also subject to these risks, and their failure to adhere to these laws and regulations also could damage our businesses or reputation or result in regulatory intervention, which could have a material adverse effect on our results of operations and financial condition.

Further, we routinely transmit, receive and store personal, confidential and proprietary information by email and other electronic means. Although we attempt to protect this confidential and proprietary information, we may be unable to do so in all cases, especially with customers, business partners and other third parties who may not have or use appropriate controls to protect confidential information.

While we maintain cyber risk insurance providing first party and third party coverages, suchthat insurance may not cover all costs associated with the consequences of personal and confidential and proprietary information being compromised. A material cyber security breach could have a material adverse effect on our results of operations and financial condition.

At December 31, 2017,2019, we had approximately 15,60018,600 employees, of whom approximately 11,40014,000 were employed within our Markel Ventures operations.