One day after iOS 8 was made available to the public, adoption of Apple’s software for mobile devices is trailing that of its predecessors. 

According to data provided by mobile marketing firm Fiksu, iOS 8 adoption is lagging as much as 50% compared to iOS 7 adoption last year. Data from mobile ad firm Tapjoy tells a similar story: “iOS 8 stands at under 6% [adoption] eighteen hours after its initial availability, while iOS 7 was at 12% after the same time period,” the company wrote in a blog post.

iOS 8 adoption is also slower than iOS 6, although the difference isn’t as drastic:

It’s not surprising that people aren’t rushing to download iOS 8 as quickly as they were to iOS 7. The latest software upgrade isn’t as much of an Earth-shattering redesign as last year’s counterpart, and considering the enormous free memory required by the upgrade, people might be holding off for a bit longer while they juggle their digital stuff to make room.

See Also: How To Download iOS 8 When Your iPhone Is Too Full Of Stuff

Older iPhone users might also be wary of the way iOS 7 treated the iPhone 4, and don’t want to be the ones to suffer this time. Multiple reports of sluggishness on older devices, including the iPhone 4s and iPhone 5, could be prompting owners of older models to hold off upgrading their software until the iPhone 6 and iPhone 6 Plus, the devices for which iOS 8 is designed, are in their hands.

Lead image by Apple; graphic courtesy of Tapjoy