https://www.polygon.com/2018/7/6/17542506/steam-games-sales-data-leak

Unlike many other parts of the entertainment industry, PC gaming is remarkably opaque when it comes to sales data. Valve Software’s Steam marketplace represents a significant portion of all PC game sales, but historically that data has been difficult or impossible to see and even more difficult to independently verify.

For the briefest of moments this week, we had a fabulously clear snapshot of the number of games Steam has actually sold. We still have the image, but it’s the last one we’re likely to get any time soon. Just a few days after a window into their organization was opened, Valve slammed it shut again.