iOS 7 Adoption Rate at 87%
Just ahead of WWDC 2014, the adoption rate of iOS 7 is all the way up to 87%. Only 11% are on iOS 6 and 2% are on earlier versions. The way we can tell what version devices are on is based on the downloads of apps from the App Store during a 7-day period. Because of this, these estimates are not the most accurate. For example, I have an iPod Touch 2 running iOS 4. It hasn’t been turned on for a long time, like many of peoples other devices running older version of iOS, so this chart isn’t that accurate since it’s based on downloads in the past seven days.
Source: Apple Developer