SQ, I think any amount of rape is a problem, it doesn't have to be rampant.
It was quite difficult to find figures for victims of female rapists, given that (1) it's under-reported and (2) females can't legally be rapists. But...
This American report from 2010 found that 1.4% of men were raped in their lifetimes (that's 1,581,000 people), and 22.2% (that's 25,130,000 people) suffered some 'other sexual violence' (pg. 19), including being made to penetrate, sexual coercion, unwanted sexual contact, and 'non-contact unwanted sexual experiences'.
The majority of male rape victims suffered under male rapists, but for the "other forms", the majority reported female perpetrators in (pg. 24):
- 79.2% of forced penetrations (4,317,192 victims)
- 83.6% of sexual coercions (5,689,816 victims)
- 53.1% of unwanted sexual contact (7,060,176 victims)
I would include forced penetrations and sexual coercions as being rapes, even if it doesn't meet the legal definition. I've certainly seen men nagging their wives into sex (coercion) being called rape here, and rightly so imo. So I would guess that those 5,689,816 male victims of sexual coercion by a female would probably see it as a problem.
An international study of college-age men and women found that "the rates of verbal sexual coercion against men by women are consistently estimated to be between 10 and 20% ... whereas physically forced sexual intercourse by women against men is estimated to be between 1 and 3%" (pg. 404)
So there are some figures.
"And why you think this is as big a problem as men raping men, women and children."
I don't, and never said it was.
"My understanding is that most rape and sexual assault is carried out by men"
Absolutely right, all the figures show this. But just because one problem isn't a big as another problem, doesn't mean it isn't still a problem, iyswim.