Adoption of iOS 9 isn't expected to be as slow as iOS 8, in part due to the smaller footprint of the update, which requires only 1.3GB of space compared to 5GB for the upgrade from iOS 7.
Still, as mobile advertising firm Tapjoy pointed out yesterday, after 18 hours iOS 9 adoption was only a tad faster than iOS 8 and still lagged iOS 7, which reached 15 percent adoption in the same timeframe. Its analysis is based on 200 million iOS devices.
Tapjoy also noted that seven percent of iPhone owners had upgraded, while four percent of iPads, and six percent of iPods had iOS 9 installed.
iOS users in South Korea were moving to iOS 9 faster than any other nation with 9.29 percent having made the move, followed by Japan at 9.52 percent. More than seven percent of devices in China, the UK, and Italy had been updated, followed by the US, Canada, and Germany at around six percent.
Differences between the speed of iOS adoption in different versions are likely to shrink in coming days. Last year, Apple's first update to its iOS distribution figures following the release of iOS 8 revealed a 46 percent takeup rate within four days of its release. iOS 7 was installed by 52 percent of US users after seven days.
Apple's most recent iOS distribution figures based on App Store measurements was on September 14 and shows that 87 percent of iOS devices are running iOS 8 while 11 percent a running iOS 7.