I always think back to my uni days where the maths department had several specific scholarships/ bursaries/ prizes for female students as part of a drive to increase gender equality. We probably had around 30% girls in my year? There were other, softer elements to the strategy and overall I reckon it was working, personally. That kind of push is probably how you start to improve demographics.

(Side note: I was however, endlessly amused that the psych course which had 2 guys and ~120 girls had no such concerns about equality...)