Quite interesting. Has there ever been a history where women couldn't or weren't allow3d to do BJJ? Also I wonder why it is? Injuries? Lack of interest? Be a good social study piece.

It's hard to say if this is actually more women dropping out of the sport, or the women's side of the sport growing and it hasn't caught up the ranks yet. I know back in my day, at competitions there was "the women's division". then, as i came up the ranks, slowly the belts and weights separate. Now, even locally, we've got all the belts separate, all the standard weight classes, and even masters! And the white belt divisions are growing, and over the years, there is more and more athletes in the blue, purple, and brown black. When I just started competing there was no female black belts or brown competing locally, now there is lots!

I choose to interpret the results positively as a growing base, instead of women dropping out.

We just ran a camp here a few weeks ago, and one of our instructors for the camp was Kris Shaw, one of the female "dirty dozen". She was telling stories of trying to find a gym in California (where she's from) back in the nineties, but got turned away multiple times because she was a woman, so I think this was really a thing at one point in time.

Props to the women who are into this sport, but I've found it hard to convince any of the ladies in my life to come roll at my gym, no matter how I sell it. Most simply don't want to have sweaty people in close contact with them, much like most guys. I think though once the sports hits a certain tipping point where women come into a gym and there are lots of other female partners to practice with, we'll see a better and more stable representation of the ladies. I can see it being hard to be the only woman in a class of guys who are on average bigger and stronger, and having to grind that out forever. Imagine you're 5'9" 175 lbs and you walk into a gym and everyone is 6'2" 250 lbs. Sure, you may continue, but it would never be as fun as rolling with people who are your skill level and size.

Anyway, I recognize that most women have physical challenges when participating in a male dominated environment, so those that persist have all my respect. They're probably harder than 90 percent of the guys who darken the doors of most BJJ gyms.

Definitely way more women in Jiu Jitsu now than 25 years ago. That said, for the moment, it’s a male dominated sport. I remember as a blue belt (many years ago now) my instructor invited the women’s national wrestling team to train with us. It was great and also the first time I had trained with women after a few years of BJJ and a youth of wrestling.

It would be interesting to see a peer-reviewed study examining the reasons behind the disparity. My guess is that it is a combination of the rationales offered in this thread.

Are the other 57% not verified or unfinished profiles? Missing some numbers here..

You're misunderstanding the numbers :) These are % of females out of total practitioners in each belt. So for instance in purple belt, there are 8% females and 92% males.