The pie chart above pretty much says it all. It looks like KitKat didn't get adopted as quickly as Jelly Bean, although it installed on almost 25% of Android devices now. While we still see a few groups of people who are still on Ice Cream Sandwich and even Gingerbread, what's really shocking is that a tiny .7% sliver of users are still sporting their crusty old Froyo. With Android L on the horizon, we expect to see Jelly Bean numbers diminish, while KitKat will probably still grow for a little while longer.
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Source: Android Developers