throughout the fourth quarter, net sales would have grown 24% compared with Q4 2007). See Item 8 of Part II, “Financial Statements and Supplementary Data—Note 14—Quarterly Results (Unaudited).” 

Net Sales and Gross Profit 

Revenue increased 29%, 39%, and 26% in 2008, 2007, and 2006, reflecting revenue growth in both our North America and International segments. Additionally, changes in currency exchange rates positively affected net sales by $127 million, $399 million, and $24 million for 2008, 2007, and 2006. For a discussion of the effect on revenue growth of exchange rates, see “Effect of Exchange Rates” below. 

The North America revenue growth rate was 26%, 38%, and 25% in 2008, 2007, and 2006. The increase in revenue in each year primarily reflects increased unit sales driven largely by our continued efforts to reduce prices for our customers, including from our free shipping offers and Amazon Prime, a larger base of sales in faster growing categories such as electronics and other general merchandise, increased in-stock inventory availability, and increased selection of product offerings. 

The International revenue growth rate was 33%, 39%, and 28% in 2008, 2007, and 2006. The increase in revenue in each year reflects increased unit sales driven largely by our continued efforts to reduce prices for our customers, including from our free shipping offers, a larger base of sales in faster growing categories such as electronics and other general merchandise, increased in-stock inventory availability, and increased selection of product offerings. Additionally, changes in currency exchange rates positively affected International net sales by $131 million, $390 million, and $18 million in 2008, 2007, and 2006. 

We expect that, over time, our International segment will represent 50% or more of our consolidated net sales. Additionally, as we continue to offer increased selection, lower prices, and additional product lines within our electronics and other general merchandise category, we expect to see the relative mix of sales from this category increase. See “Supplemental Information” below. 

The increase in gross profit in absolute terms during 2008, compared to 2007 and 2006, corresponds with increases in sales, offset by lower prices for customers including from free shipping offers and Amazon Prime. Generally, our gross margins fluctuate based on several factors, including our product, service, and geographic mix of sales; sales volumes by other sellers; changes in vendor pricing, including the extent to which we receive discounts and allowances; lowering prices for customers, including from competitive pricing decisions; improvements in product sourcing and inventory management; and the extent to which our customers accept our free shipping and Amazon Prime offers. Such free shipping and Amazon Prime offers reduce shipping revenue and reduce our gross margins on retail sales. We view our shipping offers as an effective worldwide marketing tool and intend to continue offering them indefinitely. 

Sales of products by marketplace sellers on our websites represented 29%, 28%, and 28% of unit sales in 2008, 2007, and 2006. Since revenues