I'm pretty wary of dipping a toe into these waters, but this survey Tia links to measuring what proportion of males have committed acts counting as rape has some stunning, and bizarre, findings. It discovered that "one in twelve male students surveyed had committed acts that met the legal definitions of rape or attempted rape." That said, "84 percent of those men who committed rape said that what they did was definitely not rape." And "Only 27 percent of those women whose sexual assault met the legal definition of rape thought of themselves as rape victims."
So what we're left with is eight percent of men have committed an act consonant with the legal definition of rape. But 84 percent of that eight percent either isn't aware of it, or is in denial, or is lying. And 73 percent of the women who were raped either don't believe that's what happened, or are in denial, or are lying. I couldn't find the "legal definition" of rape or attempted rape on the page explaining the study, and can't figure out if it's at variance with the study's definition, which defines rape as "being subjected to unwanted sexual intercourse, oral sex, anal sex, or other sexual contact through the use of force or threat of force."
That seems strange, though. Defining rape as unwanted sex compelled through the use of, or threat of, force, is not a weak or ambiguous definition. In order to clear that bar, there'd have to be actual force employed, or a distinct statement of intent. And if one of those conditions were met, I'd assume both parties would know, and if they were willing to admit to the incident, as they would have had to for this study, I've trouble believing they wouldn't call it rape. So what am I missing here?