I recently commented on a blog post about the gender distribution among authors in Science Fiction and fantasy. Most hard science scifi authors are male. Most fantasy authors are (with some notable and excellent exceptions) are female. Romance as a genre is almost completely dominated by female authors (with a few awful exceptions).
What gives? Simple. Everybody writes what they want to read. Men like adventure, hard science, engineering, military thrillers, and other things that gets the blood and testosterone pumping, and the brain working. Women prefer things that deal with interpersonal relationships–sociological science fiction (where the majority of female scifi writers tend to gravitate), sword and sorcery fantasy, unicorns, romance (both in the original definition and the modern one that borders on porn).
It’s not rocket surgery. And trying to set up some stupid, unattainable quota will have the same effect that title IX had on sports–punishing men, because fewer women want to do what the boys do.