A few years ago, I posted an analysis of the OGS userbase, looking at trends in growth (OGS Player Statistics). I recently returned to OGS, and asked Anoek for an updated DB to run an updated analysis, which he graciously provided.
New stats/plots are here:
Overall trends are roughly similar: growth has been consistent and healthy. About 2000 new users sign up on OGS each week, and about 5% of those will remain active beyond a year.