Apple's App Store Usage Numbers Suggest 85% Adoption Rate for iOS 7
The increasing adoption rate of iOS 7 has also led to a drop in iOS 6 usage, with the older operating system now installed on just 12 percent of devices. Three percent of devices also continue to use even older versions of iOS. In early December, iOS 7 usage was at 74 percent, jumping to 78 percent later in December and then to 80 percent in late January.
Apple's data, which comes directly from the App Store, represents the most definite iOS 7 adoption information for developers.