U.S. e-commerce sales for the first 33 days of the holiday shopping period are up 12% from a year ago, according to new data from ComScore. Sales were up 28% on Thanksgiving day, 9% on Black Friday, 16% on Cyber Monday and 9% in the latest week through December 3.

The research firm said Cyber Monday was the heaviest single online e-shopping day on record, with U.S. sales of $1.28 billion.

“Cyber Monday kicked off the most recent work week with an all-time record of more than $1 billion in e-commerce spending, representing a strong 16-percent growth rate versus year ago,” said comScore chairman Gian Fulgoni. “While we saw three more days during the week with at least $800 million in spending, growth rates slowed to single-digit levels following several weeks at about 13 percent. We believe this softening is attributable to retailers�€� heavy discounting and promotional activity during the earlier part of the holiday season [through Cyber Monday], which pulled some consumer demand forward, resulting in a mild hangover effect in the days immediately following Cyber Monday. We may see another week of this effect before late season discounts and buying by procrastinators gives the season a final spending surge.”

ComScore also noted that online spending seems to be shifting toward large retailers. For the period from Nov. 1-29, the research firm reports, sales were up 20% at the top 25 retailers, and 13% overall, while small- and mid-sized retailers saw zero growth. The top 25 controlled 67.8% of e-commerce spending versus 32.2% for smaller to mid-tail retailers.

As part of comScore's annual holiday shopping survey of consumers,
approximately 500 Internet users were asked about the importance of
social media sites influencing their purchase decisions. When asked how
much they agreed with the statement “Recommendations from friends on
social media sites are a great way to get gift ideas during the holiday
season,” 33% agreed with the statement compared to 24% who
disagreed (while 43% remained neutral). ComScore said this finding suggests
that, while social media can certainly play a role in driving holiday
shopping and purchase behavior, it may not be a primary driver for many
consumers.

When asked about which specific forms of social media may have helped
influenced their purchase decisions this holiday season, consumers
indicated that reading a consumer-generated product review (14%)
and reading an expert product review (10%) were the most likely
to influence their behavior. Some respondents also indicated that
following a fan page on Facebook to learn about deals and promotions (9%), a friend�€�s Facebook status update about a product/service (9%) and watching a product-related video (8%) influenced
their holiday purchases this season.