Here's a surprise: iOS pays out the most in ads

eCPM for iPhone is $2.85, followed by Android at $2.10.
Opera Software's State of Mobile Advertising report mined info from a global network of 35 billion+ ad impressions, which delivered more than $400 million to mobile publishers in 2012.
The browser firm bought premium ad network 4th Screen earlier this yearn, which helped it collate the stats.
The key findings are:
* The average eCPM on iPhone is £1.82 ($2.85), followed by Android at £1.34 ($2.10); Windows Phone is last at £13p ($0.20) eCPM
* Business & Finance is the top revenue category
* Performance varies significantly over very short periods of time, so publishers and advertisers should use multiple networks

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