If you’ve followed the discussion about sexual assault on college campuses in America, it’s likely you’ve heard some variation of the claim that 1 in 5 women on college campuses in the United States has been sexually assaulted or raped. Or you may have heard the even more incorrect abbreviated version, that 1 in 5 women on campus has been raped.

As two of the researchers who conducted the Campus Sexual Assault Study from which this number was derived, we feel we need to set the record straight. Although we used the best methodology available to us at the time, there are caveats that make it inappropriate to use the 1-in-5 number in the way it’s being used today, as a baseline or the only statistic when discussing our country’s problem with rape and sexual assault on campus.

First and foremost, the 1-in-5 statistic is not a nationally representative estimate of the prevalence of sexual assault, and we have never presented it as being representative of anything other than the population of senior undergraduate women at the two universities where data were collected—two large public universities, one in the South and one in the Midwest.

Second, the 1-in-5 statistic includes victims of both rape and other forms of sexual assault, such as forced kissing or unwanted groping of sexual body parts—acts that can legally constitute sexual battery and are crimes. To limit the statistic to include rape only, meaning unwanted sexual penetration, the prevalence for senior undergraduate women drops to 14.3%, or 1 in 7 (again, limited to the two universities we studied).

Third, despite what has been said in some media reports, the 1-in-5 statistic does not include victims who experienced only sexual-assault incidents that were attempted but not completed. The survey does attempt to measure attempted sexual assaults, but only victims of completed incidents are included in the 1-in-5 statistic.

Fourth, another limitation of our study—inherent to web-based surveys—is that the response rate was relatively low (42%). We conducted an analysis of this nonresponse rate and found that respondents were not significantly different from nonrespondents in terms of age, race/ethnicity or year of study. Even so, it is possible that nonresponse bias had an impact on our prevalence estimates, positive or negative. We simply have no way of knowing whether sexual-assault victims were more or less likely to participate in our study. Face-to-face interviewing tends to get higher response rates but is considerably more expensive and time-consuming. That said, given the sensitive nature of the questions, the anonymity and privacy we afforded respondents may have made women comfortable with responding honestly. Overall, we believe that the trade-offs associated with low response rates were overcome by the benefits of cost-efficiency and data quality.

To back up, it makes sense to explain exactly how a woman responding to our web-based survey—conducted in 2007 and funded by a grant from the National Institute of Justice—would get counted as a victim in the 1-in-5 statistic. In the survey, all 5,446 randomly sampled undergraduate women who participated were presented with a prompt explaining that subsequent questions would ask them about “nonconsensual or unwanted sexual contact” including:

* forced touching of a sexual nature (forced kissing, touching of private parts, grabbing, fondling, rubbing up against you in a sexual way, even if it is over your clothes)

* oral sex (someone’s mouth or tongue making contact with your genitals or your mouth or tongue making contact with someone else’s genitals)

* sexual intercourse (someone’s penis being put in your vagina)

* anal sex (someone’s penis being put in your anus)

* sexual penetration with a finger or object (someone putting their finger or an object like a bottle or a candle in your vagina or anus).

Among other items, the students, after being told they were going to be asked about their experiences with unwanted sexual contact, were asked these two key questions:

Since you began college, has anyone had sexual contact with you by using physical force or threatening to physically harm you?

and

Since you began college, has someone had sexual contact with you when you were unable to provide consent or stop what was happening because you were passed out, drugged, drunk, incapacitated, or asleep? This question asks about incidents that you are certain happened.

To be counted as a victim of sexual assault or rape and included in the 1-in-5 statistic (19.8%), a woman would have to be a senior and answer “Yes” to one or both of those questions.

In our reports, sexual-assault victims who selected only “Forced touching of a sexual nature” in a follow-up question asking about the type of contact that happened were classified as victims of sexual battery only, whereas victims who selected any of the other response options (oral sex, sexual intercourse, anal sex, or sexual penetration with a finger or object) were classified as victims of rape.

Our survey had limitations, as outlined above. However, we believe the results have value for several reasons.

First, all research of this kind faces methodological and logistical challenges, but we approached the study objectively and implemented it with as much methodological rigor as possible given the budget we were given and the state of the field at that time.

Second, our results are not inconsistent with other studies that surveyed undergraduate students about their sexual-assault experiences, and surveying students directly about their sexual-assault experiences using behaviorally specific language remains the most scientifically valid way to measure the prevalence of sexual assault. Survey data have limitations, but they are universally believed to be more accurate than official law-enforcement or campus crime data on sexual assault. A large majority of sexual-assault victims do not report their experiences to law enforcement or other authorities, so official crime statistics dramatically underestimate the prevalence of sexual assault.

Third, the study results are helping fuel a conversation about sexual assault on college campuses, a problem that likely exists at most colleges—not just the two with which we collaborated—and it negatively impacts many thousands of students every year. We are pleased to be part of this conversation and to see attention being paid to this issue, especially since there seems to be ample room for improvement in terms of how universities, service providers, law enforcement and the justice system go about trying to prevent victimization, encourage reporting, meet the needs of survivors and respond to reported incidents.

What we are perhaps most excited about is that additional research is currently being conducted that will build and improve upon what has been done to date. For example, at RTI, we are working on a new study with the Bureau of Justice Statistics, the Office of Violence Against Women, and the White House to develop a survey instrument and methodology for collecting valid and reliable data on campus climate and sexual assault.

Although there will never be a definitive estimate of the prevalence of sexual assault, these new research efforts are larger in scale and are employing scientific best practices, which will result in methodological improvements that should increase the validity and utility of the findings. With these methods and the knowledge we gain along the way, we can begin to envision a meaningful research agenda, which could involve collecting data from students at many universities, perhaps on an annual or ongoing basis, creating nationally representative as well as university-specific estimates.

Christopher Krebs and Christine Lindquist are Senior Research Social Scientists at RTI International, an independent, nonprofit research institute. They are both in the Center for Justice, Safety, and Resilience at RTI, and they directed the Campus Sexual Assault Study, which was funded by the National Institute of Justice and completed in 2007.

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