by Claudia Bruemmer

ComScore reported that Internet retailers made over $1 billion in online sales on four of the five workdays last week. That means ecommerce is almost 15 percent ahead of last year for this holiday season, although growth is slowing a bit compared to the frenzy around the Thanksgiving weekend.

Holiday season retail sales for November 1st through Friday, December 16th, totaled $30.937 billion, up 14.95 percent from $26.914 billion during the same period last year, according to comScore, which estimates retail sales based on tracking the online activity of a panel of 1 million U.S. consumers.

The most profitable online shopping days last week was Monday, with sales reaching $1.13 billion and Friday, the day that 2,300 e-retailers took part in the Free Shipping Day promotion organized by FreeShipping.org. Shoppers responded by spending $1.07 billion at retail web sites.

ComScore indicated the year-over-year growth rates for major e-retail promotions have slowed in the past couple of weeks. For example, Friday − Free Shipping Day − was up 14 percent over 2010, and last Monday − which marketers dubbed Green Monday − was up 19 percent. By contrast, the Friday after Thanksgiving, known as Black Friday, had an increase in online sales of 26 percent over the same day last year, and sales the following Monday, which is called Cyber Monday, were 22 percent ahead of 2010. So far, Cyber Monday was the heaviest online shopping day of 2011, at $1.251 billion.

Although there may be a few more heavy online sales days yet this week, comScore chairman Gian Fulgoni said, “It’s clear that we have now reached the crescendo for this season and that spending will begin to slow as we get closer to Christmas, leaving Cyber Monday as the top-ranked shopping day for the second year in a row.”

ComScore also notes that free shipping offers rebounded last week, with 56.0 percent of online buyers carrying no shipping charges for the week ended Friday, December 16, up from 52.2 percent during the same period last year. Last week’s percentage also represented an increase from 53.0 percent for the week ended December 11, 2011; 59.4 percent for the week ended December 4; and 64.4 percent for the week ended November 27, which was the Sunday of Thanksgiving weekend.

“This season has seen a continuation of the trend where an increasing percentage of transactions involve free shipping, as more consumers demand it and more retailers provide it,” said Fulgoni. “During the week of Thanksgiving and Cyber Week we saw at least three in five transactions use free shipping, significantly higher rates than we’ve ever previously observed.” Cyber Week is the week following Thanksgiving weekend.

Another company tracking the sales of some 500 major online retailers reported that e-retail sales were up 10.8 percent for the week ended December 11 over the same week in 2010 at those ecommerce sites. IBM Corp.’s IBM Benchmark survey, based on data from its Coremetrics analytics unit, reported mobile devices accounted for 12.1 percent of site traffic during that week, an increase of 5.0 percent over a year earlier, and that 8.9 percent of those retailers’ sales came from smartphones and tablets, up from 3.8 percent last year. IBM predicts online sales will grow in December by 9.5 to10 percent over December 2010.