Horace Dediu has taken a look at the platform growth of the major smartphone operating systems in the US. The prettiest picture is for Apple.

An observation from yours truly, and it’s not the point of his post by any means, is that Apple’s problem isn’t one of screen size. In the US market, customers must have hundreds of larger options than the iPhone from which to choose, and they’re choosing the iPhone at a more rapid rate than ever. Apple’s problem with Android competition is in the rest of the world where the subsidized market doesn’t play.

Apple’s number one iPhone priority needs to be on a lower cost model for these markets. I’m sure they know that.