The number I care about (which I haven't been able to find, not that I looked very hard) is how many unique (per user) app installations there were per month fo

The number I care about (which I haven't been able to find, not that I looked very hard) is how many unique (per user) app installations there were per month for each platform. The number of users is only useful if users of all platforms install apps at the same rate, which my intuition says is not true. Many android phones are sold as "the nice phone that you can get with your 2-year contract" as opposed to an item that the owner sought out explicitly, so they're less likely to explore the full potential of the device.