The cited study: http://www.bjs.gov/content/pub/pdf/rsavcaf9513.pdf It points out that students are very unlikely to report rape to the police, but somehow assumes that they will answer questions about it on a survey. It also shows wide variations from one year to another. It's not a bad study, but the data doesn't really inspire confidence.
Edit: from page 3 "From 1997 to 2013, females ages 18 to 24 consistently experienced higher rates of rape and sexual assault than females in other age brackets."
and from page 4: "However, there was no significant difference in the rates of female students and nonstudents who experienced attempted rape or other sexual assault. This suggests that differences in the rates of completed rape largely accounted for differences in the overall rates of rape and sexual assault between students and nonstudents."
The Instapundit is attempting to debunk public-health assessments of the incidence of sexual assault with crime-report data, when a key argument of anti-rape activists is that rape/sexual assault largely goes unreported. And given the way that women are treated who make allegations of domestic violence, sexual assault, and sexual harassment, I would not be surprised if that is correct.
The study cited in that link (which I link directly below) says 20% of students who admitted to being raped said they reported it to police, compared to 32% of non-students.
Edit: from page 3 "From 1997 to 2013, females ages 18 to 24 consistently experienced higher rates of rape and sexual assault than females in other age brackets."
and from page 4: "However, there was no significant difference in the rates of female students and nonstudents who experienced attempted rape or other sexual assault. This suggests that differences in the rates of completed rape largely accounted for differences in the overall rates of rape and sexual assault between students and nonstudents."