A latest report from mobile ad network InMobi shows that mobile ad impressions on Android devices eclipsed Apple's iOS devices in January, representing 37% of all U.S. mobile ad impressions on its network versus 23% for the iPhone.
Android's share jumped a full 21 percentage points since InMobi's last report in Oct'10. Android actually passed the iPhone for the first time in December. The iPhone's overall share of mobile ad impressions actually dropped 1.3%.
InMobi only measures ad impressions on its own network. Although a majority of its 5.9 billion North American ad impressions in January (58%) came from the mobile Web rather than apps, so these numbers should be fairly representative. And 4.1 billion of those ad impressions came from smartphones, nearly double from October.
Globally, Nokia and Symbian OS phones still make up a larger share of InMobi's ad network, with 20% and 18% share, respectively. The iPhone is third globally with 16%, and Android has 14%. Android's share globally grew 8.6% since Oct'10, whereas the iPhone's growth slowed to 1.7%.