As expected, Windows 10's usage share growth sank after Microsoft ended the free upgrade it had offered customers for the past year.

According to analytics vendor StatCounter, Windows 10's week-over-week gains in the first two weeks of August were 0.13 and 0.15 percentage points, respectively. The increases were the smallest of any two-week span this year, with the exception of two different times -- in April, again in July -- when Windows 10's share fell from one week to the next.

If the remainder of August plays out the same as the first half, Windows 10 will post a one-month increase about a third of July's and approximately a fourth of June's.

StatCounter measures usage share, an indicator of online activity and not representative of the actual number of users running the OS.

The growth slowdown was about as certain as death and taxes: The expiration of the free upgrade meant consumers, and businesses without volume license agreements, would have to pay $110 and $200, respectively, to put Windows 10 on a PC.

Minus the free upgrade, growth will come from companies transitioning from Windows 7, and consumers and businesses buying new PCs equipped with Windows 10. Neither will be a factor in the short term.

Although most large organizations have dabbled with Windows 10, few have begun migrating significant numbers of their devices to the OS. Those migrations are not expected to begin until the fourth quarter of this year, and not peak until 2017-2018. Meanwhile, new PC shipments continue to remain in an historic slump, with consumers declining to refresh their aged hardware and corporations waiting until next year to increase purchases.

Microsoft's latest claim for Windows 10 was made seven weeks ago, when an executive said that there were 350 million devices running the OS. Although growth has slowed, Microsoft has pledged to update that number: Last month, CEO Satya Nadella told Wall Street analysts that his company would "regularly report the growth of Windows 10 monthly active devices."