December retail figures in the US are set to top last year’s total thanks to a late surge in spending by consumers, according to research business ShopperTrak.

Sales for the week ending 17 December were up 21.7% on the previous week and 1.3% year-on-year, leaving month-to-date figures up 0.5% on December 2010.

However, the weekend of 16-18 December showed a slight decline in sales on last year, including a 0.7% decrease for “Super Saturday” – the last Saturday with regular shopping hours before Christmas.

ShopperTrak, which analyses data from more than 25,000 locations across the US, believes that the extra Saturday between Thanksgiving and Christmas may have tempted shoppers into delaying their purchases.

“December’s retail gains will likely continue all the way through Christmas and the end of Hanukkah,” said ShopperTrak founder Bill Martin. “As the weather gets colder and these important days get closer, retailers should be ready to service customers looking to buy.”