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What We Know About Sexual Assault in College — And What We Don’t

Last week California Gov. Jerry Brown signed a law requiring the state’s colleges and universities to have “affirmative consent” policies, which means students would have to get conscious, voluntary consent from their sexual partners. The law addresses a problem without much reliable data: sexual assault among students.

“There hasn’t been any mechanism to accurately and completely collect” data on sexual assault in college, and prevalence of consent-based defense of sexual-assault accusations, said Jennifer Gentile Long, director of AEquitas, a Washington, D.C.-based nonprofit group that develops prosecutor practices for cases of sexual violence against women. “There are also many barriers to obtaining the information.”

Added Cassia Spohn, a professor of criminology and criminal justice at Arizona State University: “The data we have are woefully inadequate.”

It’s hard to quantify just what proportion of sexual-assault trials are disputes over consent — the law’s focus. “There is no nationwide data collection on the use of this defense,” Long said in an email. “Based on professional experience prosecuting sexual-assault cases, as well as the combined experience of our staff (over 100+ years), as well as providing assistance to prosecutors across the country on this issue over the last 10 years, this is the defense in the overwhelming majority of cases.”

Consent so often becomes the defense, said Dean G. Kilpatrick, director of the Medical University of South Carolina’s National Crime Victims Research and Treatment Center, because the other two common defenses — there was no sexual assault, or someone else did it — are rarely viable. Claiming a case of misidentity has become even less viable because of genetic evidence.

One challenge in compiling data on college crime is that university police handle some cases, while local police handle others. Some media coverage of the law has referred to assault “on campus.” But nearly all sexual assault of college-age victims occurs off campus, and the bill specifically covers assault “both on and off campus.”

Callie Rennison, co-director of the Criminology and Criminal Justice Research Initiative at the University of Colorado, Denver’s School of Public Affairs, investigated the location of sexual assault on college-age Americans by aggregating results from the National Crime Victimization Survey. It’s a Bureau of Justice Statistics poll of Americans about crimes against them — including crimes they haven’t reported, and crimes that they themselves don’t perceive as crimes.

Since the crime-victimization survey doesn’t separate college students from those who don’t attend college, Rennison examined responses from people ages 18 to 25, a standard research technique. She found last week, in results that haven’t yet been published, that 97.7 percent of all rape and sexual assault of people in that age range happened off campus, including 100 percent for male victims and 97.3 percent for female victims. Nearly two-thirds of the time, the location was the victim’s home or a friend’s home.

Of course, not all 18- to 25-year-olds are students. But even if just 20 percent are, and they account for all on-campus sexual assault, nearly 90 percent of sexual assault of college students would be happening off-campus.

Rennison’s data is aggregated from surveys between 1995 and 2012. “By aggregating, one gets more stable estimates,” she said in an email. “Year to year, these types of numbers do not change appreciably.”

Her findings don’t mean students who live on campus are safer than those who aren’t. A 2004 study of surveys of more than 23,000 women at 119 schools found that students who lived on campus, particularly in sorority houses, were more likely to be victims of sexual assault.

Many researchers turn to surveys because official stats miss the unreported cases. Those represent most cases — especially in college. Kilpatrick was the lead author on a 2007 Justice Department-funded survey of 5,000 women that found 16 percent of victims of all ages reported rape to law enforcement compared to just 12 percent of college students. And just 6 percent of college students who were assaulted with alcohol involved reported the incident to police.

Carl Bialik was FiveThirtyEight’s lead writer for news.