The way this research is conducted is astonishing: Men were simply surveyed and asked whether they had ever had sex with someone who didn’t want to. Remarkably, men repeatedly said, yes, they had.

One of the most chilling sections of Krakauer’s book quotes a fraternity brother, “Frank,” describing his technique to a researcher, David Lisak:

“We’d be on the lookout for the good-looking girls, especially the freshmen, the really young ones. They were the easiest. ... Then we’d get them drinking right away. ... They’d be guzzling it, you know, because they were freshmen, kind of nervous.”

Image Brian Banks during a preseason game with the Atlanta Falcons in 2013. Credit... David Goldman/Associated Press

“Frank” recounted how he targeted one young woman, plied her with alcohol-spiked punch, and then led her to a bed. “At some point, she started saying things like ... ‘I don’t want to do this right away,’ or something like that. I just kept working on her clothes ... and she started squirming. But that actually helped, because her blouse came off easier. ... She tried to push me off, so I pushed her back down. ... I mean, she was so plastered that she probably didn’t know what was going on, anyway. I don’t know, maybe that’s why she started pushing on me. But, you know, I just kept leaning on her, pulling off her clothes.”

“Frank” said he kept his arm across her chest, by the base of her neck, to reduce her squirming as he had sex with her. When he was finished, he dressed and returned to the party.

And the woman? “She left.”

There are no easy solutions, but one way to fight the epidemic is legal: Prosecute aggressively, while recognizing that sexual encounters are often complex, ambiguous, fueled by alcohol, and prone to he-said-she-said uncertainties.

Another way to fight back is cultural: Blunt conversations among men and women alike about consent, alcohol, and the need for friends to step up with what’s called “bystander intervention.” That means that just as you don’t let a friend drive drunk, you don’t let a friend take advantage of someone — or let a plastered friend get steered to a predator’s bed.