• by Mark Walsh  @markfwal, June 5, 2012

Recent research from mobile ad network Millennial Media showed that ad impressions from tablets and other connected devices increased to 20% in the first quarter, up from 15% a year ago.

Mobile rich media ad provider Medialets released separate research today that also indicates wider diffusion of mobile ads. The company said 40% of rich media campaigns it delivered in the first quarter ran across different platforms -- handsets, tablets, apps, the mobile Web, and Android and iOS operating systems --compared to 20% in the year-earlier period.

Both sets of figures underscore the rising adoption of tablets -- which have 15% to 20% adoption in the U.S. so far -- as well as smartphones, which have increased to almost 50% share among mobile users, up from 36% a year ago. More smartphones and tablets also mean more people using apps, mainly on Android and iOS devices, which helps explain the expansion of mobile advertising across more platforms.

Among other findings, Medialets found that rich media ads on tablets were 30% more likely to include video -- which makes sense because they have larger screens than smartphones. Ads that feature video, in turn, had an average of 35% higher engagement. And ads that include video, a brand-related game or product catalog can push time spent with an ad to over one minute.

Among rich media ad formats, expandable banners are by far the most common, making up 64% of the total on phones and 60% on tablets. Regular banners and interstitial ads account for the balance of ads, with the former more prevalent on tablets. In terms of performance, expandable banners had an engagement rate of 15% and a click-through rate of 1.2%, while interstitial ads had comparable figures of 8% and 3%.

Looking just at tablets, expandable banners had an average engagement rate (including the tap to expand the ad) of 17% versus 10% for interstitials, which typically appear when an app launches or between rounds of a game.

The Medialets first-quarter research also analyzed rich media ad response rates across three key industry categories: automotive, entertainment and finance. Entertainment ads had had the highest click-through rate, at 2.8% compared to .9% for finance and .5% for automotive. (The company noted that auto ads often include landing page features in ads, eliminating the need for a click-through.)

Finance ads had the highest overall engagement rate (including click-throughs) at 15%, followed by entertainment (12.5%), and auto (11.5%). Finance also high the highest ad expand rate -- at 1.8%, slightly ahead of auto (1.5%), and entertainment (1.2%).