The 2011 holiday shopping season was a banner year for online retail, which broke numerous records. Savvy retailers can pat themselves on the back; the best have become incredibly adept at enticing consumers and delivering a great customer experience.

But they’ll probably also want to thank their spend on search according to a new report by IgnitionOne, which found that significant increases in this area for Q4 boosted impressions, clicks and transactions.

According to IgnitionOne, it saw a 14% increase in search spend in Europe, which translated to a 22% increase in clicks and 19% increase in clickthroughs.

The numbers were even more impressive in the US, where retailers specifically boosted their search spend by 26% in Q4. That produced a 42% jump in impressions, a 42% boost in clicks and a 67% increase in transactions.

IgnitionOne’s Chris Evans pointed out the obvious implication that despite increasing spend levels, search spending is also getting more efficient.

With increasing transactions per pound spent; essentially brands are getting more bang for their buck.”

The ability of search spend to drive meaningful action jives with Baynote’s recent Annual Holiday Online Shopping Experience Survey, which found that, despite the hype around social and mobile, search is still one of the two biggest drivers of sales.

But IgnitionOne’s study does raise the interesting question of how retailers will gain from mobile search ads in the future.

It observed a 317% year-over-year increase in mobile search ad impressions last year, and saw 24% of all search ad spend on Black Friday going to mobile.

With this in mind, it will be interesting to see whether mobile search ads are soon just as important to retailers are web search ads.