QVC Inc. and its subsidiaries (unless otherwise indicated or required by the context, the terms "we," "our," "us," the "Company," and "QVC" refer to QVC Inc. and its consolidated subsidiaries) includes the reportable segments of QVC-U.S. and QVC-International (combined referred to as "QVC-Global", which does not constitute a separate reportable segment) as well as HSN Inc. ("HSN"), which became a subsidiary of QVC as of December 31, 2018 as explained in more detail below. QVC curates and sells a wide variety of consumer products via highly engaging, video-rich, interactive shopping experiences, distributed to approximately 404 million worldwide households each day (including our joint venture in China as discussed below in further detail) through our broadcast networks as well as our over-the-top platforms (such as Apple TV, Roku and others), our websites (including QVC.com, HSN.com and others), our mobile applications and our social pages. We believe we are the global leader in video retailing, e-commerce, mobile commerce and social commerce, with operations based in the United States ("U.S."), Germany, Japan, the United Kingdom ("U.K."), Italy and France. Additionally, we have a 49% interest in a retailing joint venture in China, which operates through a television shopping channel with an associated website. The joint venture is accounted for as an equity method investment. Our operating strategy is to create premier shopping destinations for our customers across multiple broadcast, digital and emerging platforms (featuring fresh, relevant and compelling product selections and programming), further penetrate our core customer base, generate new customers and expand internationally to drive revenue and profitability. For the year ended December 31, 2018, approximately 93% of QVC's worldwide shipped sales were from repeat and reactivated customers (i.e., customers who made a purchase from us during the prior twelve months and customers who previously made a purchase from us but not during the prior twelve months). In the same period, QVC attracted approximately 4.4 million new customers and the global e-commerce operation comprised $5.8 billion, or 51%, of QVC's consolidated net revenue for the year ended December 31, 2018.
QVC's consolidated net revenue decreased 3.9% for the three months ended March 31, 2019 as compared to the corresponding period in the prior year. The three month decrease in net revenue is primarily due to a 3.1% decrease in units sold, $36 million in unfavorable foreign exchange rates across all markets and a slight decrease in average selling price per unit ("ASP"), which was partially offset by a $22 million decrease in estimated product returns, primarily driven by the decrease in sales volume at QxH.
During the three months ended March 31, 2019 and 2018, the changes in revenue and expenses were affected by changes in the exchange rates for the U.K. Pound Sterling, the Euro and the Japanese Yen. In the event the U.S. Dollar strengthens against these foreign currencies in the future, QVC's revenue and operating cash flow will be negatively affected.
In discussing our operating results, the term currency exchange rates refers to the currency exchange rates we use to convert the operating results for all countries where the functional currency is not the U.S. Dollar. We calculate the effect of changes in currency exchange rates as the difference between current period activity translated using the prior period's currency exchange rates. Throughout our discussion, we refer to the results of this calculation as the impact of currency exchange rate fluctuations. When we refer to constant currency operating results, this means operating results without the impact of the currency exchange rate fluctuations. The disclosure of constant currency amounts or results permits investors to understand better QVC’s underlying performance without the effects of currency exchange rate fluctuations.