It seems to have plateaued and increasing more slowly. Combining data from Steam and Statcounter reveals this:
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Good point, thanks. The way I modeled the adjustment was by assuming that most usage is captured by Statcounter but there's movement back and forth to a reservoir that flies under its radar, in bursts, with zero net movement in the long run. So I used a geometric mean of the source data scaled by the square root of their averaged ratio.