According to data released by Kantar Worldpanel ComTech on Tuesday, iOS accounted for 51.2 percent of all U.S. smartphone OS sales for the 12-week period ending on Dec. 23, 2012, up over 7 percent from 44.9 percent in 2011.

Apple’s increased performance appears to be at the cost of Android as Google’s mobile OS marketshare declined from 44.8 percent in quarter four 2011 to 44.2 percent over the same period in 2012. Also seeing a contraction in marketshare was beleaguered BlackBerry maker RIM, which suffered a drop from 6.1 percent of smartphone sales in the last quarter of 2011 to 1.1 percent during the same period in 2012.

“In particular, 36% of iOS sales were derived from other smartphone users over the last year,” said Kantar Worldpanel ComTech analyst Mary-Ann Parlato. “While this figure remains stable over time, the proportion of Android users moving towards the Apple brand increases. 19% of iOS sales over the last year were derived from Android users, compared to 9% in 2011.”

So if this set of results is correct, it appears the iPhone 5 was more popular than envisaged. In a few days time we will find out for sure.