Latest Android OS only on 7.5 percent of phones
The latest report from Android Developers details the percentage of handsets which are currently using the various operating systems and have recently logged onto the Google Play Store, and Marshmallow has just 7.5 percent of the share.
Now if we were talking about the latest Apple operating system that would seem like a fault with users not upgrading their handsets but it's more complicated when it comes to Android - mostly because it's down to the device manufacturer to actually offer the update.

