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FORTUNE — According to the latest full day’s report from Mixpanel’s handy little widget, 71% of iOS device owners had upgraded to iOS 7 by Monday, 27 days after Apple (AAPL) released it.
Last year, it took 30 days of iOS 6 to reach a record 61% penetration.
By contrast, Windows 7 is still at less than 50% four years after Microsoft (MSFT) shipped it, according to NetApplications. That’s because Windows 7 is still competing with Windows XP, a 12-year-old operating system that runs more that 30% of the world’s PCs.
Apple hasn’t said how many of the 700 million iOS devices it has sold since 2007 are still in operation, but Mixpanel’s chart suggests that on Sept. 23, when Tim Cook announced that iOS 7 downloads had passed 200 million, the number of active iOS devices was roughly 350 million.
That means that as of Monday, 250 million were running iOS 7.