After announcing iOS 7 at WWDC 2013, Apple recently added a graphics chart on developer site that can be accessed by public. The chart shows percentage of each iOS version used by iDevices today. Previously, Google has posted similar graphics chart for Android on Android developer site.
From the charts on both developer sites, you can see a big difference of operating system version distribution. 93% of iPhone, iPod Touch, and iPad are running on iOS 6, which is the latest iOS version available at this time. 6% of iDevices still use iOS5, and 1% use older iOS versions.
For Android, the most popular mobile operating system currently, most of Android devices still run the old Android 2.3 Gingerbread released in the late of 2010. Jelly Bean is on the second place with 33%, followed by ICS on the third with 25.6%. About 4.8% use older versions such as Froyo, Eclair, and others.
We can conclude that iDevices don’t experience fragmentation problem, one of weaknesses on Android. Apple also hopes that iOS 7 adoptions will be smooth, so it will be easier for developers to focus on latest operating system without thinking about previous versions compatibility.