Windows 8.1 users have been half again as likely to upgrade to Windows 10 as their compatriots running Windows 7, data from a Web metrics vendor showed today, confirming expectations about who would upgrade first to Microsoft's new operating system.

The ascension of Windows 10's usage share has largely come at the expense of Windows 8.1, according to measurements by Irish analytics company StatCounter. Of the combined usage share losses posted by Windows 7, Windows 8 and Windows 8.1 since the last full week before Windows 10's July 29 launch, 57% has been attributed to Windows 8.1 deserters.

Windows 7, meanwhile, contributed 37% of the losses by the last three editions, and Windows 8, 6%.

The disparity was not unexpected: Most pundits and analysts figured that users of Windows 8.1 -- like Windows 7, eligible for a free upgrade -- would be first in line to dump their existing OS and migrate to the new. The changes in Windows 10, including the restoration of the Start menu and windowed apps, were most attractive to Windows 8 and 8.1 users, experts believed, because their removal had been widely panned.

Simply put, Windows 7 users, who were more satisfied with the OS Microsoft gave them, would be less motivated to upgrade. That's been proven out by StatCounter's early numbers.

But there were recent signs that Windows 7 users have begun jumping to Windows 10 in numbers nearly equal to Windows 8.1.

During the week of August 10-16, the difference between the declines in Windows 7 and Windows 8.1 was the smallest it's been since Windows 10's debut. In that week, Windows 7 lost 0.55 percentage points of usage share, only slightly less than the 0.64 percentage points given up by Windows 8.1. The week before -- August 3-9 -- the gap between the two was much larger: Windows 7 lost 0.95 percentage points, while 8.1 declined by 1.42 points.

StatCounter's data also illustrated just how important Windows 7 conversions will be to Windows 10's ultimate success -- as Microsoft has defined it, that would mean 1 billion devices running the operating system by mid-2018. Even if it coaxed every Windows 8 and 8.1 user into upgrading, Microsoft would be looking at a usage share of less than 21% for Windows 10. It must convince large segments of Windows 7's base to migrate as well.

That may require modification of the Windows 10 pitch, perhaps with less talk about the return of the Start menu, say, and more about enhanced security. Working against Microsoft are a plethora of Windows 10 behaviors, particularly its mandated updates and the concurrent loss of control over what reaches customers' devices and when. That has raised hackles among the traditionalists who stuck with Windows 7.