In's 10-k filing with the SEC, the e-retailer reports that, while the company continues to increase its direct purchasing from manufacturers, it still sources a "significant" amount of inventory from "relatively few" vendors. Three vendors accounted for about 21% of all inventory purchases last year, with Ingram Book Group being Amazon's single largest vendor, accounting for more than 10%—roughly $225 million—of inventory purchases. Word among publishers is that Amazon relied heavily on Ingram to fill holiday orders.

Amazon's Marketplace option, which offers used and new products for sale, has quickly become an important selling vehicle; it accounted for 12% of U.S. retail orders last year, compared to "nominal" sales in 2000. The success of Marketplace, along with improvements in inventory management and product sourcing, helped boost the company's gross profit margin to 27% in 2001, from 25% in 2000.