Mobile advertising optimizer Smaato has released clickthrough rates and fill rates for its global mobile ad network for the month of May. Smaato’s metrics are based upon 40 mobile ad networks and over 7 billion ad requests served in the Smaato Network of more than 5,000 registered mobile publishers in May 2010.

The figures show that Android is starting to recover in terms of global clickthrough rates (CTR) and that feature phones have closed the gap on Symbian, looking set to take top spot in June if the current growth rate is maintained. In the US, Smaato’s metrics reveal that Symbian still dominates the region in terms of CTR – despite a small market share of handsets. Android has now leapfrogged Apple in to second place, as Apple suffers another drop in global CTR.

Smaato’s CTR Index consists of the average CTR of all devices, with the average set to 100. Symbian still leads in terms of CTR globally, with a small improvement to 159 from 157 in April. Feature phones increased to 147 from 134 in April, while Android also showed signs of recovery as it increased to 40 from 39 in April. Windows Phone (54) and Apple (55) suffered significant drops from the previous month, while Palm and Blackberry also continued their downward trend.

Smaato’s metrics also demonstrate the performance of mobile ad networks globally, including the fill rate, which is defined as the percentage of ads delivered per ad request and varies by different factors, like country, device and content type.
The fill rates of the global top 10 ad networks, dropped again, with the global average dipping to 21 per cent, compared to 26 per cent in April and 28 per cent in March. Eight ad networks performed above the average, but the gap between the best, with a fill rate of 96 per cent, and the second best, with 53 per cent, is huge. It rises from 13 percentage points in April to 43 percentage points this time.

The average for worldwide ad network fill rate performance has been in decline since February. Smaato says this data helps to prove that an ad network aggregation system can help partners achieve the best possible return and the highest possible fill rates, across the globe.
The report also looks at the response time of the top-performing ad networks. The fastest response time in May was measured at 39 milliseconds (ms) compared to 11 ms in March and 25 ms in April. In May, there was a significant difference between the top eight ad networks, with only 34 milliseconds separating the best and eight best, in comparison to the ninth best, which came in at 197 ms.

There’s more information, and more stats, here.