End is Nigh dev uses achievement stats to determine Steam sales data

Valve isn't alone in wishing Steam Spy was more accurate, but The End is Nigh developer Tyler Glaiel beat it to the punch on at least one solution. Today, he revealed that he shared code with the sales tracking site that he says will improve the accuracy of its data across most games, then open sourced the code for anyone to use.

In a Medium post, Glaiel explains that he first discovered the idea through the site barter.vg, a digital game library tracker and tradeable bartering site. The site suggested that achievement data could be used to determine how many people had purchased a given game: for example, if "50% of players" had an achievement, then there were at least two total. 33% meant at least three, and so forth. If two achievements existed, one with 50% and one with 33%, then at least six players must exist.

Glaiel connected with a development group that noticed Steam's API giving 16 digits of precision on achievement data, which meant a far larger number of players could be accurately accounted for. There was some trouble with inaccuracies on games that had large numbers of users such as PUBG and Team Fortress 2, but with some experimentation and math, Glaiel solved it. The end result was code that, according to Glaiel, offers a higher degree of accuracy than Steam Spy could provide at the time.

"The thing that's interesting about this method is that it returns exact numbers," Glaiel said. "The old method Steam Spy was using required random sampling of user profiles and extrapolating the data to fit the whole steam audience from that. It was accurate but included some pretty big error bars, especially for games with low numbers of sales. The new achievement based method doesn't have this weakness. There is no random sampling or uncertainty here, the tool spits out the exact number valve is using to calculate achievement data, and it does it on a snapshot of data instantly instead of requiring collecting data over time. You don't need a server to use this method, you can just run a simple script and get an answer in seconds."

Glaiel shared the code with Steam Spy last weekend and it is currently being used on the site. The assistance is timely; Steam Spy was temporarily shut down in April due to a Steam API update, though creator Sergey Galyonkin was able to bring the site back in a limited capacity.

Yesterday at White Nights 18 in St. Petersburg, Valve business development head Jan-Peter Ewert stated that Valve was currently working on something "better than Steam Spy" for sales tracking, citing the site's inaccuracies as reason to provide "new tools and new ways of getting data out of Steam."