[clarkm]

Yeah, that would provide a much clearer picture. Though I'd guess that the iOS/Android market share is highly correlated with the dominant wireless carriers in the area. Since iPhones were initially exclusive to AT&T, I'd expect areas with a high percentage of AT&T users to have the most iOS users. When smartphones were first becoming popular, users on other carriers (e.g. Verizon) didn't have the option of purchasing iPhones, so they purchased Androids.

And this distribution probably still holds today, since most users don't switch back and forth between both operating systems.