@Seadoomaiden - The IBA tends to focus on achievements in what's collected. (types of rides, etc) For the Iron Butt Rally, you will find some sub categories
HERE that you may find interesting.
As a microcosm of all IBA certificate holders, within the eStore Database started on 04/01/20 there are:
9113 "Mr." entries
29 "Dr." entries (all male)
966 "Ms." entries
6 "Mrs." entries
This breaks down to 10.6% female riders. The older list of
Certified Ride Finishers, (which doesn't use any identifiers for sex of the rider) has many more women riders listed. Most rides do have first and last names there, but you'd have to create a search that would separate male and female names, which would still have outliers like men named Kim or where only initials are used. And since each ride is listed, there are many duplicates for each rider's name.
I suspect that the overall breakdown of the ~80k Certified Ride Finishers will have a bit smaller representation of female riders, despite women being part of this sport from the very beginning.