I'm curious if the maintainer stats include demographics such as race, gender, etc. An open project where anyone who wants to contribute may do so would provide a sociologically interesting set of data points which could be useful in targeting STEM curriculum or highlighting success stories we don't yet realize.
There's no one keeping track of that as far as I know, but the group picture of kernel maintainers (just picked the first one google brought up) is fairly informative on your questions.