Operating system iOS 11 is currently installed on 76% of all active supported devices.
The new data was published at App Store on April 22nd and is now available to developers today. On iOS 10, 10% of active devices continue to work, while older versions are installed on only 5% of devices that do not support iOS 11.
As of January 18 this year iOS 11 were installed on 65% of active devices, i.e. the number has grown by 11% over the past three months. This was probably aided by the release of versions iOS 11.2 in December and iOS 11.3 in March.
For comparison, the latest version Android 8.0 Oreo is installed on only 4.6% of devices using the Google Play services. This data does not include smartphones with Android that use third-party app stores instead of Google Play. Most smartphones with Android run on OS versions that are already several years old.