SAN FRANCISCO: Adspend dedicated to social on the Kenshoo ad platform increased by 50% year-on-year in the fourth quarter of 2015 as marketers turned to Facebook and Instagram over the holiday season.

Spend on search advertising – which comprises almost half of all US internet adspend, according to Warc's own data – grew by 8% year-on-year over the same period.

The results were revealed as part of Kenshoo's Digital Marketing Snapshot: Q4 2015, which analysed 550bn ad impressions from more than 3,000 advertiser and agency accounts.

Mobile continued to be the main growth driver for both channels, Kenshoo said, and it accounted for nearly all of the 8% spend increase in paid search.

Although year-on-year adspend growth on social far exceeded that of search – a ratio of about six-to-one – the report still highlighted that Google Product Listing Ads accounted for 26% of all paid search impressions in Q4 2015, up from just 8% in the same period the year before.

"The fourth quarter has long been about holiday sales, and the reliance on Product Listing Ads and Dynamic Product ads this season highlights the importance marketers placed on direct response ad types," said Chris Costello, director of marketing research at Kenshoo.

"On top of the new social ad types, changes in bidding strategies in the social channel refocused advertisers on smaller quantities of highly targeted clicks to drive downstream actions rather than engagement.

"This aligned with retailer sales goals during the holiday shopping season across all digital efforts to drive healthy performance improvements."

Looking at the social advertising statistics in further detail, it emerged that social clicks increased 30% year-on-year, although there was a -16% fall over the quarter.

Social click-through rates also declined in Q4 2015, by 20%, but that compared with a 64% rise over the year. Meanwhile, social impressions increased 4% over the quarter, but fell 21% year-on-year.

The cost per thousand impressions (CPM) for social ads rose to a high of $3.51 during Q4 2015, the report found, while that for search dipped slighted from the previous quarter to $13.45.

Data sourced from Kenshoo; additional content by Warc staff