So Valve has plugged up the last little hole in their API able to provide sales data for games on Steam. While making Steam profiles private by default a while back pretty much killed SteamSpy one method still remained until just a few days ago. By doing some pretty hilarious math to the global achievement data people have managed to calculate very accurate player numbers with a few major caveats:
But this method only works for games with developer-defined Achievements, so it covers about 13,000 of the roughly 23,000 games now on Steam.
It’s not exactly clear how Valve defines this “Achievement denominator,” which approaches but doesn’t precisely match up with the “players” statistics provided to individual developers. The new data also gives no indication of how many people own the game without having played it. And, in very rare cases, this method could come up with a denominator that’s off by a factor of two, thanks to common factors (though this chance becomes vanishingly small in games with more than a few Achievements).
Bolded part probably immediately invalidates the list as being accurate sale numbers but probably a fair enough assessment of how games sold comparatively to each other. Of course, any number these could also have real inflated values from being on sale at 95% off or something at some point.
The article has a sample of the top selling games at the end but also provides a link to the full list here as a CSV file:
http://www.arstechnica.com/wp-content/uploads/2018/07/games_achievements_players_2018-07-01.csv
(you can just open the downloaded file in your web browser to easily have a look at it)
For a fun and depressing time Ctrl-F your favourite games to see how much less they sold then Nekopara.
Probably the last time we’re able to get data like this unless Valve is real generous with their promised upcoming of sales data tool