Despite the fact that social ad spend is expected to double by 2016 and analysts are increasingly bullish on native social ads, search continues to be the go-to channel for advertisers looking to drive ROI.

The record-breaking holiday shopping season is making that abundantly apparent. While sales driven by social referrals have thus far been miniscule, early analysis of Black Friday sales data by search and analytics consulting firm NetElixer finds that search ads are killing it.

According to NetElixer’s study, which looked at data from 38 large U.S. retailers and 120m search ad impressions, revenue driven by paid search on Black Friday rose an impressive 31% year-over-year as advertisers invested 21% more in search ads than they did in 2011.

Mobile making an impact

NetElixer’s findings provide further confirmation that retailers ignoring mobile are likely missing out. Of the sales driven by paid search, NetElixer saw 15% coming from mobile. Last year, just 4% of sales from search came from mobile.

That creates some challenges for retailers.

Year-over-year, Black Friday average order values (AOV) have increased ever so slightly (3%) despite an 8% increase in the average number of items added to cart. With average cost per click increasing by a double-digit percentage (12%), retailers will not only need to monitor their paid search campaigns closely, but also make sure that they’re doing everything they can to maximize AOVs and minimize cart abandonment.

Mobile, for obvious reasons, complicates the latter as many if not most retailers are still perfecting their mobile customer experiences. With this in mind, savvy retailers will be paying close attention to their sales data this year, looking for insights that will help them ensure that when the 2013 holiday shopping season rolls around, they’ll be able to convert their mobile paid search traffic — which will almost certainly be higher yet again — even more effectively.