ComScore, Inc. released its Q3 2011 U.S. retail e-commerce sales estimates, which showed that online retail spending reached $36.3 billion for the quarter, up 13 percent versus year ago. This growth rate represented the eighth consecutive quarter of positive year-over-year growth and fourth consecutive quarter of double-digit growth rates.

“The third quarter of 2011 saw a continuation of the year's strength in U.S. retail e-commerce spending, even in the face of renewed economic headwinds and uncertainty facing the U.S. consumer," said comScore chairman Gian Fulgoni. "As we approach the critical holiday shopping season, we are optimistic about the continued health of the e-commerce sector despite other factors – including stubbornly high unemployment and volatile financial markets – currently weighing on the economy. More consumers than ever before are relying on the online channel for product and pricing  information, which along with the Internet's fundamental appeal of convenience and attractive pricing, are contributing to the sustained upward momentum in e-commerce spending."

The top-performing online product categories were Digital Content & Subscriptions, Event Tickets, Jewelry & Watches, Consumer Electronics and Computer Software. Each category grew at least 15 percent vs. year ago.

The 13-percent growth in the quarter was primarily a function of an increase in the number of buyers (up 22 percent), with 74 percent of all Internet users making at least one online purchase in the quarter.

40 percent of e-commerce transactions included free shipping, down from a peak of 49 percent in Q4 2010. Free shipping rates tend to peak during the holiday season.