post-1990 - something goes completely wacky in the industry and women are driven out of computing in large numbers; younger women don't even enter the field.
So, since you seem to be a younger dude perhaps you could explain exactly what it is that happened 1990-2000 that made the field so undesirable to women.
The internet happened. Online venues (like slashdot) became places where self-selection happens. Being mostly male to begin with, that's the direction online forums went. More and more pure. This is where people exploring an interest in technology go, and learn it's a field where it's acceptable to say the kind of shit that gets up-moderated here. Fewer women enter the field. Online forums become more pure. Rinse and repeat.