Measured in terms of number of unique apps†, the Top 5 categories in the U.S. app store have been Games, Books, Entertainment, Travel and Utilities. But comparing categories in terms of number of apps doesn’t capture the challenge of developing applications in different categories. As I noted in an earlier post, it’s much easier to develop a Book app than an interactive game.
One crude measure for the relative complexity of developing apps across categories is to compare the number of apps per seller. The Top 5 categories in Nov/2009, were Books (17 apps per seller), Travel (6 apps per seller), Education (4 per seller), Reference and Sports (3 per seller). There were also 3 apps per seller in the Games and Entertainment categories in Nov/2009:
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(†) Data for this post was for through 12/10/2009, and covers the U.S. iTunes App store.