The new data derivation method, as ably explained in a Medium post from The End Is Nigh developer Tyler Glaiel, centers on the percentage of players who have accomplished developer-defined Achievements associated with many games on the service. While Valve has now closed this inadvertent data leak, Ars can still provide the data it revealed as a historical record of the aggregate popularity of a large portion of the Steam library. A recently discovered hole in Valve's API allowed observers to generate extremely precise and publicly accessible data for the total number of players for thousands of Steam games.
