• by Laurie Sullivan , Staff Writer @lauriesullivan, September 27, 2012

Marketers allocated 16.3% of total search budgets to U.S. mobile search campaigns in Q3 2012 -- up from 14% in the year-ago quarter, according to a report released Thursday.

It turns out that the segment saw a 167% year-on-year increase fueled by tablet users spending 30% more time on sites and engaged with content about 20% more compared with PC users, according to the IgnitionOne Q3 2012 Online Advertising Report IgnitionOne, which highlights growth in search spending and mobile advertising.

Tablet devices accounted for 52.2% of the total mobile search advertising budget for the quarter, dropping sequentially from 60%. Apparently, marketers spent more on search ads for smartphones.

Smartphone users, while representing a larger overall audience, had on average 4% lower engagement scores compared with PC users, and 11% fewer page views. IgnitionOne attributes that to slower speed and less optimal browsing experience on a smartphone compared with larger devices.

Overall, marketers spent 17.8% more on paid search campaigns, up from 15.5% sequentially. The YoY increases in clicks continued to decelerate, up only 6% YoY compared with 13.2%, sequentially. Click-through rates (CTR) dropped by 13.7% YoY, while impressions accelerated with a YoY 22.9% increase.

Total cost per click rose 11.2%. CPCs on Google rose 7.7% YoY, the first time in 2012, but Yahoo and Bing saw CPCs rise at nearly triple the rate, at 26.1% YoY. Marketers also spent more on the Yahoo and Bing network, rising 38.8% compared with 13% YoY on Google, according to the report.

Among the $30 billion in combined brand revenue that IgnitionOne supports, Google held steady sequentially in Q3 2012, with 79% market share, compared with Yahoo and Bing at 21%.