The main part of the report does not include information about "white-box" tablets (i.e. those great selling, mostly Chinese tablets that sell so well on Amazon).
With those included, market share is: Android 52%, iOS 41% and interestingly, 7% for Windows 8.
Looking on Amazon, the Windows 8 usage seems to come from x86 tablet/laptop hybrids. Apparently there is a niche market for people that want tablet/"real" Windows functionality in one device.
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