Linux and Chrome OS could explain some of the difference...
If Windows 7 share is dropping off a bit, those people could be moving to Linux, if they are individuals or businesses without specialist applications.
Windows 8.1 buyers, who find the system difficult to use, may be getting advice from tech savvy relatives or friends to install linux in the form of ubuntu or mint. Those without help installing it, might have taken the PC back to the store and bought a chromebook.
Chromebooks are great for individuals and they are great travel PCs too. They are cheap, light weight, have a long battery life and if you spend all your time online in the browser, they are a great alternative to Windows.
I would like to see the same 2 agencies release numbers for Linux and Chrome OS on the same chart.
Biting the hand that feeds IT
