• by Laurie Sullivan , Staff Writer @lauriesullivan, March 3, 2011

Marketers by now know the fast pace at which mobile continues to scale in the United States. Now the question remains: How will consumer behavior change as search evolves on handsets and tablets? Macquarie Equities Research and Efficient Frontier released results of a joint study Thursday that highlights search advertising spend patterns. A webinar to explain the findings will follow on Friday.

Efficient Frontier manages about $1 billion in search marketing budgets annually for clients, of which 4.2% goes toward mobile -- up from 0.5% in 2010. By the end of 2011, Macquarie Equities estimates that companies will spend somewhere between 7.0% and 9.5% of search advertising dollars on mobile devices.

Efficient Frontier has anecdotal evidence that some advertisers suggest as much as 10% to 15% of all Internet search traffic comes from mobile devices today. Macquarie Equities expects that percentage to increase in time, and sees no structural reason why mobile ad spending should not at the very least achieve parity with mobile usage.

The report points to comments by Google that suggest that nearly 30% of queries coming from mobile devices originate from certain categories such as restaurants. Consumer Electronics, Beauty & Personal, Finance/Insurance, and Autos have seen between 14% and 16% mobile queries.

The report highlights a notable difference between mobile and desktop search metrics. Mobile searches have a click-through rate 30% lower than desktop, but the cost per click is slightly higher than CPCs on desktops -- 13%, according to Efficient Frontier data. Given the lower return on investment (ROI) generated by mobile ad campaigns, Macquarie Equities Analysts Ben Schachter and Tom White believe it leads to the thinking that mobile now supports branding campaigns for many advertisers. The typical revenue-based definition of ROI is a less scrutinized metric for branding-based campaigns, according to Schachter and White.

Lower conversions for mobile search campaigns result in ROI about 10 times below desktop search campaigns, according to Efficient Frontier's data. Schachter and White say this is a critical issue that marketers and advertisers will need to address as mobile growth continues to accelerate.

Schachter and White believe mobile search has attracted primarily brand advertisers. ROI measurement for mobile search advertising remains largely based on the same revenue-based ROI criteria used to evaluate desktop search campaigns, which means the statistics for mobile campaigns are often significantly lower than those running on the desktop.

The study suggests that until advertisers can more accurately attribute a wide range of successful events such as offline store visits, offline and (delayed) online sales, and phone calls to a mobile ad campaign, marketers using a traditional ROI-based approach to make campaign budget decisions will be less willing to increase mobile ad budgets. Early adopters, of course, excluded.