U.S. retail e-commerce sales for the first quarter of 2007, adjusted for seasonal variation and holiday and trading-day differences but not for price changes, reached an estimated $31.5 billion - an increase of 18.4 percent (±4.5%) from the $26.6 billion in the first quarter of 2006, according to the Census Bureau of the Department of Commerce, writes MarketingCharts.

The first quarter 2007 e-commerce estimate increased 3.0 percent (±1.3%) from the previous quarter's $30.6 billion. E-commerce sales in the first quarter of 2007 accounted for 3.2 percent of total retail sales.

"Missing from the Commerce Department numbers are sales on eBay.com that could be construed as retail sales. Some observers believe that could be about 60% of eBay sales, which translates into about $31 billion," writes Internet Retailer.

MarketingCharts offers up some additional data.