19% of Android users regularly download one or more paid apps a month — compared to 50% of iPhone users and 40% of iPod touch users, reports AdMob's July 2009 Mobile Metrics Report, a compilation of data from over 1,000 iPhone, iPod touch and Android users.

The research examines the purchasing patterns of paid applications at Apple's App Store an Google's Android Market.

Those that don't buy paid apps on either platform demonstrate similar downloading and spending habits to the ones that do. However, the most-cited reason users purchased applications was because they liked the free version of the app — demonstrating that free-to-paid conversions fare well in the app market.

Other highlights:

• Most mobile app downloaders run searches for applications directly on their mobile device, rather than from their own computers.
• Android and iPhone users download close to 10 new apps per month; iPod touch owners download an average of 18.
• As mentioned above, upgrading from the "lite" (that is, free) version of an app was the top reason users gave for purchasing a paid app.
• iPhone and iPod touch users are two times more likely to purchase paid apps than Android users.
• Regular paid app downloaders spend about $9 on an average of five paid downloads per month.

Overall, iPhone represented 60% of US smartphone usage in AdMob's network for the month, followed by RIM and Android devices (13 and 12%, respectively). And over half of Android/iPhone users spend over 30 minutes per day using their apps of choice.

The survey covered 1,117 respondents over the course of one week, spanning iPhone, Android and iPod touch uesrs across over 7,000 mobile sites and 3,000 applications in AdMob's network.

In June 2009, Google unveiled AdSense for iPhone and Android applications.