It turns out that Steam users in Asian cyber-cafes were being over-counted
A surprising resurgence in the popularity of Windows 7, and a marked drop in Windows 10, was reflected in the November 2017 Steam Hardware and Software Survey. At first glance it looked like gamers were ditching the (relatively) new version of Windows for the tried-and-true stability of good ol’ Win7, but Paul suggested a different theory: That the explosive popularity of Playerunknown’s Battlegrounds in China had thrown the balance out of whack.
He was mostly right. It wasn’t just an influx of Chinese users that caused the sudden surge, however, but an “over-counting” of people accessing Steam via “cyber cafes” in Asia.
“Historically, the survey used a client-side method to ensure that systems were counted only once per year, in order to provide an accurate picture of the entire Steam user population. It turns out, however, that many cyber cafes manage their hardware in a way that was causing their customers to be over counted,” Valve explained in a message posted above the most recent survey results.
“Around August 2017, we started seeing larger-than-usual movement in certain stats, notably an increase in Windows 7 usage, an increase in quad-core CPU usage, as well as changes in CPU and GPU market share. This period also saw a large increase in the use of Simplified Chinese. All of these coincided with an increase in Steam usage in cyber cafes in Asia, whose customers were being over counted in the survey.”
A fix has since been deployed, and users counting should now be accurate. And it appears to be working: The March 2018 survey (via the Wayback Machine) indicated that 57 percent of Steam users were using Windows 7 64-bit, followed by 36 percent on Windows 10 64-bit. The current survey basically flips those numbers: Windows 10 64-bit is back on top at 53 percent, while Windows 7 is back in second place at 36 percent.