Thanks Martin. On a per-chapter level, we can extract some more interesting numbers from meetup.com. For example, for the Berlin chapter, these are at https://www.meetup.com/opentechschool-berlin/stats/ (you might need organizer privileges to see them, not sure).
To me, the most interesting graph is this one about our active and total membership in the Berlin chapter:
Also, it is waaay outdated, but I once prepared this: Who are our Berlin learners? Some data If there is any benefit to a more recent similar analysis, or some other, I’d be happy to help out.