@tchambers Thanks for sharing! Here is a back-of-the-envelope calculation for the whole Fediverse, using data from fedidb.org:
Assuming that Monthly Active Users (MAUs) are the relevant quantity, and assuming further that there is at least one admin or moderator per server, the ratio is (1 million) to (27 thousand) which is approximately 1/37.
Take that with a pinch of salt though, it is but a very crude estimate which averages over wildly differently-sized instances etc.
(EDIT: *May* data)