Nielsen is now measuring the penetration and reach of apps on Android and iOS handsets in the US. The idea is the measure "actual consumer behavior" (rather than survey responses) based on usage patterns of 5,000 US smartphone owners who've agreed to participate.
Other data captured will be: frequency, duration, and size of total audience. Below are some of the data released by Nielsen to promote the new service, showing reach of various apps on Android smartphones:
Between men and women there are some differences. For example, among female Android users, Facebook is the most heavily penetrated Android app after the Android Market itself.