Every certain period of time Apple updates the percentage of users in each version of the operating system, collecting data from downloads of apps in the App Store. This is how we can know the evolution of iOS 11.
According to data collected by Apple from the adoption of the operating system, as of November 6, 52% of devices in the market use iOS 11. This means that more than half of users have already installed iOS 11 on your iPhone or iPad. On the other hand, iOS 10 continues in a total of 38% of the devices, while the remaining 10% is iOS 9 and earlier versions (usually devices compatible with the latest versions).
The funny thing in this case is that the adoption of iOS 11 is lower than expected. That is, last year iOS 10 on these same dates had about 60% while two years ago iOS 9 in the same period of time and had a 66% adoption. The problems of iOS 11 in its launch? More non-compatible devices? Perhaps a cluster of all the factors has resulted in this lower adoption.
iOS 11 takes a total of 51 days available for everyone, since it was released on September 19. It remains to see how it ends at the end of the year, since iOS 10 reached a maximum of 89% of the devices, and that will be difficult to overcome. Anyway, to understand the context, Android Oreo which is the latest version of Android, is installed on 0.2% of devices.