Using a loophole in the statistics of gaming achievements, Ars Technica calculated the approximate number of game owners on Steam. The most popular game in the store turned out to be Team Fortress 2, which has more than 50 million owners.
Recall that this method of counting game owners was invented by indie developer Tyler Glaiel. He gave his code to the Steam Spy service, and also posted it in the public domain. A few days later, Valve, which is developing its counterpart Steam Spy, closed the loophole.
As it turned out, Valve reacted too late. The calculations published by Ars Technica are by far the most accurate open data on how many players have purchased a particular game. They take into account all gamers who have opened at least one game achievement.
The top 20 games looks like this:
The full list of more than 13 thousand games can be downloaded from this link.
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