5.4% of paid search impressions in the US come from mobile devices

"It is clear that mobile is not just a growing market, it is a market to really dive into. Mobile is interesting for both search engines and for advertisers. Research performed (in the US!) by Efficient Frontier shows us that the number of mobile searches and mobile paid ads is growing rapidly. But CTR and ROI still stays behind.
Efficient Frontier tells us that already 10-15% of traffic on average comes from mobile devices. And that’s an average, if you look at specific markets these numbers can sometimes even double. The research also shows that 5.4% of all paid search impressions currently come from mobile devices, which is a huge growth compared to last year. This means that by the end of 2011 Efficient Frontier believes that “somewhere between 7.0%-9.5% of search advertising dollars could be spent on mobile devices”."

Source:  Research performed by Efficient Frontier, reported in State of Search, 10th March 2011