https://wccftech.com/ios-12-adoption-rate-48-hours/

Given how iOS 11 turned out to be, it’s not surprising that people are a little reluctant to update their devices to iOS 12.

iOS 12 is a huge update when it comes to performance improvements, especially on older devices. But after just 48 hours of its release, the OS is installed on just 10% of total devices. If you compare things straight with iOS 11, the OS was installed on 10% of devices in just 24 hours. In 24 hours, iOS 10 was installed on 14.45% of devices. These numbers come courtesy of Mixpanel.