lease arrangements, repurchase common stock, pay dividends, or repurchase, refinance, or otherwise restructure our debt for strategic reasons or to further strengthen our financial position. 

The sale of additional equity or convertible debt securities would likely be dilutive to our shareholders. In addition, we will, from time to time, consider the acquisition of, or investment in, complementary businesses, products, services, capital infrastructure, and technologies, which might affect our liquidity requirements or cause us to secure additional financing, or issue additional equity or debt securities. There can be no assurance that additional lines-of-credit or financing instruments will be available in amounts or on terms acceptable to us, if at all. 

Results of Operations 

Beginning in the first quarter of 2015, we changed our reportable segments to North America, International, and AWS. These segments reflect the way the Company evaluates its business performance and manages its operations. See Item 1 of Part 1,“Financial Statements—Note 11—Segment Information.” 

Net Sales 

Net sales include product and service sales. Product sales represent revenue from the sale of products and related shipping fees and digital media content where we record revenue gross. 

Sales increased 20% , 20% , and 22% in 2015 , 2014 , and 2013 , compared to the comparable prior year periods. Changes in foreign currency exchange rates impacted net sales by $(5.2) billion , $(636) million , and $(1.3) billion for 2015 , 2014 , and 2013 . For a discussion of the effect on sales growth of foreign exchange rates, see “Effect of Foreign Exchange Rates” below. 

North America sales increased 25% , 23% , and 26% in 2015 , 2014 , and 2013 , compared to the comparable prior year periods. The sales growth in each year primarily reflects increased unit sales, including sales by marketplace sellers. Increased unit sales were driven largely by our continued efforts to reduce prices for our customers, including from our shipping offers, sales in faster growing categories such as electronics and other general merchandise, increased in-stock inventory availability, and increased selection of product offerings. 

International sales increased 6% , 12% , and 14% in 2015 , 2014 , and 2013 , compared to the comparable prior year periods. The sales growth in each year primarily reflects increased unit sales, including sales by marketplace sellers, offset by the unfavorable effect of foreign exchange rates. Changes in foreign currency exchange rates impacted International net sales by $(5.0) billion , $(580) million , and $(1.3) billion in 2015 , 2014 , and 2013 . Increased unit sales were driven largely by our continued efforts to reduce prices for our customers, including from our shipping offers, sales in faster growing categories such 

as electronics and other general merchandise, increased in-stock inventory availability, and increased selection of product offerings. 

AWS sales increased 70 %, 49 %, and 69 % in 2015 , 2014 , and 2013 , compared to the comparable prior year periods. The sales growth primarily reflects increased customer usage, partially offset by pricing