Without question, Amazon is the growth engine for online retail in the United States. U.S. e-commerce grew by $58.6 billion in 2017, per U.S. Commerce Department figures, and Internet Retailer estimates the gross merchandise value of goods sold through Amazon-owned sites grew $42.61 billion. That means Amazon accounted for about 72.7% of U.S. e-commerce sales growth last year, up from 65.9% in 2016.
A significant portion of the gross merchandise value of goods sold through Amazon in the U.S. is sold by marketplace sellers: 48.2%, according to Internet Retailer estimates. Amazon collects a commission on each sale made by marketplace sellers. The commission varies from 8%-25% according to the product type, with most products requiring a 15% commission.
Putting that into context of overall U.S. e-commerce sales, the total value of sales made by U.S. marketplace sellers on Amazon accounted for 20.1% of U.S. online sales last year, up from 17.4% in 2016.