• by Laurie Sullivan  @lauriesullivan, July 9, 2015

Search engine marketers in the United States continued to make double-digit investments in paid-search advertising during the second quarter of 2015. Investments rose 22% compared with the year-ago quarter, but down from 26% sequentially. The report, released by IgnitionOne Thursday, signals three consecutive quarters of gains.

U.S. marketers spent 22% more for campaigns running on tablets; and 71% on phones, year-over-year (YoY), with smartphones seeing the largest leap at 59%. The cost per click continues to rise on mobile devices. Those on phones rose 24%, and tablets, 26%.

The Yahoo-Bing network gave back market share. After three quarters of growth, the combined companies lost U.S. search market share in Q2, returning to 24.5% of share compared to Google’s 75.5% of U.S. paid-search spend.

Click-volume growth remained low, rising 6% in the quarter. The Yahoo-Bing network saw clicks rise 25%, while Google clicks grew 1% in Q2 compared with the previous year-ago quarter. IgnitionOne attributes the growth to the switch to Enhanced Campaigns and Yahoo’s November deal with Mozilla to be the default search engine on Firefox.

Overall, impressions fell 13%, largely due to more advertisers pulling out of the Google Display Network where advertisers have experienced poorer efficiency, according to the report. Google impressions fell 21% year-over-year, but the Yahoo-Bing network saw an increase of 12% YoY.

The cost per click (CPC) rose 15% YoY across the board, but down from 21% in the prior quarter.

Overall, click-through rates rose 22%, which translates to 35% on Google and 24% on the Yahoo-Bing network. The overall rate fell from 30% in Q1 2015.

The findings also report on programmatic display for Q2 2015, which rose 33% in spend, compared with the year-ago quarter. IgnitionOne said the decrease in impressions seen in past quarters due to Facebook changes has tapered off, resulting in a drop of 1% overall. Impressions rose 60%; and spend, 47%.