• by Laurie Sullivan  @lauriesullivan, January 13, 2016

Impressions from U.S. paid-search advertising campaigns running on Google rose 7% in the fourth quarter of 2015, compared with the previous year, after declining 21% in the prior quarter. Clicks rose, but the cost per click saw its smallest growth during the quarter for the year, according to research released Wednesday.

While this quarterly research released from IgnitionOne finds that search spend has not returned to the overall peak seen in Q1 2015, it does continue to climb steadily. The biggest issue in the quarterly report, the metrics are sourced solely from Google, unlike past reports that included Bing and Yahoo. The company says the recent partnership changes for Yahoo and Bing made it difficult to accurately discern trends from those engines.

Aside from the switch in partners and cloudy numbers, IgnitionOne attributes the rise in impressions on Google in the U.S. to a combination of seasonality, increase in Google Partnership Network activity, and Google’s changes to shopping ads, which created an increase in impressions as a result of adding the carousel feature that visually dominates the majority of mobile screens when users search. This allows more ads to appear on-screen, resulting in higher impressions.

The acceleration of mobile search spend in the U.S. slowed in the fourth quarter of 2015, up 34% compared with the year-ago quarter. Search spend on tablets rose 19% YoY, compared to the third quarter, which remained relatively flat. IgnitionOne attributes the increase in tablet spend to seasonality, as well as Google’s move to handle tablet search ads in a way that is more similar to mobile search as opposed to desktop.

Interestingly, especially during the Thanksgiving weekend, mobile experienced what the report calls a significant decrease in spend and CPCs compared with 2014. It demonstrated the greatest increase -- 35% -- in impressions YoY, compared with desktop at 9.5% and tablet at 12%.

Marketers in the fourth quarter of 2015 spent 44% of their mobile budget on tablets vs. 56% on phones, among IgnitionOne clients. During the quarter impressions on phones rose 15% clicks 70%; spend, 34%; and CTR, 47%; and CPCs fell 21%. Impressions on tablets fell 18%, while clicks fell by 3%, spend rose 19%, CTRs rose 18%, and CPC rose 23%.

Education during the quarter had the highest CTR of any vertical at 133%, although impressions fell 52%, and spend rose 5%. Clicks rose 7% and CPC fell 2%.