40% of rapists are women

Look at the CDC’s 2010 National Intimate Partner and Sexual Violence Survey. The first thing to note is that the NIPSVS decided that men being forced to have sex with women isn’t rape. Let’s think about this again. The NIPSVS finds that men are the majority perpetrators of rape. 98% of female rape victims and 93% of male rape victims had a male perpetrator. A woman shoving her fingers up a man’s anus is rape, but a woman shoving her vagina down on his penis is not. The latter is not classified as rape, but as “made to penetrate” and is placed in the category of “other sexual violence”.
If you read the report yourself it is very clear that “being made to penetrate someone else” is considered not to be rape.
It is stated outright on page 84 with the following sentences (my emphasis):

Being made to penetrate is a form of sexual victimization distinct from rape that is particularly unique to males and, to our knowledge, has not been explicitly measured in previous national studies.

This idea that it’s not rape is not incidental, it’s intentional. Take a look at this article by well-known feminist rape researcher Mary P. Koss in which she underlines the importance of not counting male rape as rape unless the man have been penetrated:

It is inappropriate to consider as a rape victim a man who engages in unwanted sexual intercourse with a woman.

The exact definitions of rape and “being made to penetrate someone else” used in NISVS 2010 can be found on page 17 in the report.
If we look at the more reliable statistic, the risk of rape in the last twelve months, and we fix the NIPSVS’s mistake in classifying forced envelopment as “other sexual assault” and not rape, we find that 80% of men report a female rapist and 98% of women report a male rapist. (This estimate is based on the sex of reported perpetrators for sexual assault over a lifetime. There is no reason to think the number of female perpetrators for ‘forced envelopment’ would decline between the lifetime and last year reports: if anything they would increase)
Since there were roughly equal numbers of men(forced to penetrate) and women(forced to envelop) raped in the last year, if we look at a population of 100 rape victims, 50 of which are male and 50 of which are female and apply the statistic that 80% of the male victims were raped by a woman, we get 40 male victims raped by a woman.
That works out to about 40% of rapists being female and 60% being male. A far cry from 95+% of rapists being male (When same-sex rape is excluded the ratio becomes 44/56 male/female rapists. One reason why same-sex rape should be excluded for an accurate picture of the gender proportions of rapists is because male-on-male rape may be inflated relative to female-on-female rape due to the large population of incarcerated and formerly incarcerated men. The greater rate of male-on-male rape may be a byproduct of more men cycling through society’s rape-camps (otherwise known as ‘prisons’) at a greater rate then women.).

 http://dontneedfeminism.com/post/71294252715/40-of-rapists-are-women-yes-get-over-it