• by Mark Walsh  @markfwal, January 10, 2012

In its final benchmark report for the holiday season, IBM said mobile sales in December doubled to 11% of digital sales from 5.5% a year ago, while mobile traffic nearly tripled to 14.6% of all sessions on a retailer’s site from 5.6% during the year-earlier period.

Driving the most mobile traffic to retail sites were the iPhone and iPad, which accounted for 5.2% and 4.3% of visits, respectively. Meanwhile, the iPad proved to the be the leading to device when it came to m-commerce, with conversion rates reaching 6.3% versus 3.1% for all other mobile devices.

Online retail sales overall were up 7.5% in December compared to last year, according to the IBM data. Department stores and categories including health and beauty, home goods and apparel all saw double-digit online sales gains over last year. Online retail activity didn’t stop on Christmas Day, when Internet shopping increased by 16.4% over 2010.