Search marketing budgets in the United States increased 31% during the 2011 holiday shopping season compared with last year, according to new figures from Kenshoo Inc., a vendor of software that helps manage paid search and online marketing programs.

The spending figure covers spending on Google, Bing and Yahoo between Nov. 1 and Jan. 2, and involves an analysis of 28 billion search ad impressions, 350 million clicks and 8 million online sales transactions, Kenshoo says.

For every dollar spent on paid search during that period, retailers received $5.57 back from online sales, it says. “The 2011 holiday shopping season in the U.S. was a true battle for retailers with search advertising competition reaching new heights,” says Aaron Goldman, Kenshoo’s chief marketing officer. “Kenshoo customers were prepared, capitalizing on increased consumer shopping activity during key dates and taking advantage of the growing role of mobile devices as shopping tools.”

14% of clicks during the holiday shopping season came from consumers using mobile devices such as smartphones and tablet computers—which themselves accounted for 8% of clicks, Kenshoo says. Consumers using tablets had a 2.72% conversion rate, more than the 0.87% conversion rate for consumers with smartphones. Of those consumers with smartphones, shoppers using Apple devices converted at a rate that was 20% higher than consumers whose smartphones rely on the Android operating system, Kenshoo adds.