App Annie Intelligence, which tracks more than 700,000 apps, reports that freemium apps – free apps that have in-app purchases – are experiencing impressive revenue growth worldwide, far outpacing premium apps in both iOS and Google Play stores. Over the last 24 months, worldwide revenues for freemium apps on iOS have more than quadrupled. In 2012, worldwide revenues on Google Play have grown 3.5X. Now, apps generate 69 percent of the worldwide iOS app revenue and 75 percent of global Android app revenues. Meanwhile, premium revenues for both app stores remained relatively flat in these time periods.