• by Steve Smith , Staff Writer @popeyesm, August 20, 2012

Even as the tagging and tracking technologies for mobile ad platforms lag considerably behind those online, many performance marketers are embracing real-time bidding. International mobile ad server MoPub reported its quarterly results late last week, showing that demand for mobile inventory is rising at a breakneck pace. Just between Q1 and Q2 2012, the average bids per ad request were up 300%. The bids per ad or "bid depth" reflect the level of competition for ad impressions now coming from demand-side platforms (DSPs).

MoPub is only one of many RTB exchanges on the market with metrics that represent only exchanges made on its system. But the company claims the data comes from 15 billion monthly ad impressions served in the U.S., Europe, Asia and Latin America. The exchange is managing mobile app inventory in iOS and Android.

The MoPub metrics offer a number of interesting clues about the trajectory of ad rates, inventory and ad formats among mobile media buyers.

For instance, while iOS continues to command higher eCPMs (89% higher), Android has gained considerably in impression volume. In June, iOS average eCPM was $.80 versus $.43 for Android. But the Google OS saw its share of auction volume increase from 28% in MoPub’s exchange in April to 39% in June. Nevertheless, in terms of average eCPM, iOS continues to track 23% higher and Android 34% lower across the last two months measured.

When it comes to eCPMs internationally, while many countries pay less than U.S. advertisers, Italy (+2%), Great Britain (+5%), Japan (+8%), and Canada (+9%) pay more. And Spain (+24%) and Australia (+24%) pay much higher eCPMs.

When it comes to format prices, the iPad clearly is the place where publishers want to play. While eCPMs for standard 320x50 smartphone banners stood at $.61 in June and full-screen interstitials were at $2.21 and $.82 (horizontal versus vertical orientation), an iPad banner was selling at $1.01 eCPM and iPad full-screen interstitials were selling at $4.47 and $1.62 eCPM (horizontal versus vertical orientation).

The good news for publishers is that digital magazines and robust tablet apps are showing real promise in replacing some of their dwindling print and even online ad rates. At least for now.