Not a huge surprise that The Tavern is an older, mostly male crowd. The initial D&D / RPG community was nearly all male and nostalgia for Old School Gaming is still strong.
How about The Tavern's Facebook Community?
Lets look at ENWorld:
ENWorld is a much younger community. The percentage of women is twice that of The Tavern yet still doesn't hit 8%.
How about RPG.net?
RPG.net hits 9% for its female audience. Much like ENWorld, it skews younger.
I couldn't find basic demographics for Roll20, which I think would have been the most insightful.
In any case, those are the numbers.
edit - this is the best I could find for Roll20 and Fantasy Grounds:
Also, this for Roll20:
and this for FG2