Bureau of Justice Statistics conducted a survey of college students for the 2014-15 school year. The sample size was 15,000 women and 8,000 men from 9 schools. The average response rate for women in all 9 schools was 54%, exceeding the expected 40% response rate for women. The average response rate for men in all 9 schools was 40%, exceeding the expected 35% response rate for men. More details about the methodology:

Nonresponse bias analyses were conducted at the school level using detailed student roster data provided by the schools. Minimal bias was detected (i.e., differences in characteristics of respondents and the population of eligible students) and survey data were adjusted or weighted to compensate accordingly. The survey data were thoroughly reviewed for quality and completeness. Only about 2% of respondents started but did not finish the survey, and the level of missing data (i.e., the proportion of survey items not answered by survey respondents)
was also relatively low for most items. In addition, the CCSVS used representative samples of students at eight of the nine schools to obtain female prevalence estimates of sexual assault within the desired level of precision (Goal 2). In other words, the precision for the prevalence estimates for sexual assault experienced during the 2014–2015 academic year exceeded the design goal of a 9% RSE at all schools except one.

According to Figure 48, the data shows that women are often perpetrators of rape/sexual assault, too. It found that when it comes to any kind of sexual assault, whether it's rape through physical force, groping, rape through incapacitation, threatening to harm, etc., women were barely less likely than men to have done any form of sexual assault (2.9% of men and 2.7% of women). When it comes to touching and grabbing in particular, 2.5% of college men and 2.4% of college women were perpetrators, a minuscule difference. College men and college women are just as likely as each other to have threatened to harm someone in terms of sexual assault (0.6% for both), and college women were slightly more likely than college men to have used physical force before to rape or sexually assault someone (0.8% of women and 0.6% of men). They're equally likely to have raped/sexually assaulted an incapacitated individual (0.7% both). Admittedly, according to Figure 47, college men were more likely than college women to perpetrate sexual harassment (4.4% of college men and 2.9% of college women). Although women are less likely to commit sexual harassment, they perpetrated more than half the amount that men did. Women did not comprise a minuscule percentage of sexual harassment perpetrators.

A lot of feminists argue that 1 in 5 college women are sexually assaulted, but this is a myth. It's not 1 in 5. According to Christina Hoff Summers:

This incendiary figure is everywhere in the media today. Journalists, senators and even President Obama cite it routinely. Can it be true that the American college campus is one of the most dangerous places on earth for women?

The one-in-five figure is based on the Campus Sexual Assault Study, commissioned by the National Institute of Justice and conducted from 2005 to 2007. Two prominent criminologists, Northeastern University’s James Alan Fox and Mount Holyoke College’s Richard Moran, have noted its weaknesses:

“The estimated 19% sexual assault rate among college women is based on a survey at two large four-year universities, which might not accurately reflect our nation’s colleges overall. In addition, the survey had a large non-response rate, with the clear possibility that those who had been victimized were more apt to have completed the questionnaire, resulting in an inflated prevalence figure.”

Fox and Moran also point out that the study used an overly broad definition of sexual assault. Respondents were counted as sexual assault victims if they had been subject to “attempted forced kissing” or engaged in intimate encounters while intoxicated.

Defenders of the one-in-five figure will reply that the finding has been replicated by other studies. But these studies suffer from some or all of the same flaws. Campus sexual assault is a serious problem and will not be solved by statistical hijinks.

The real percentage of college women who get raped in a span of 4 years is actually about 1.9%, according to a Bureau of Justice Statistics study of college-age women from 1995-2013. Even CDC's survey of women showing that 1 in 5 are raped has similar limitations. According to Bureau of Justice Statistics' 1987 report of an estimated lifetime victimization rates for certain types of crime, they made an estimate of what percent of people are victims of a certain type of crime in their lifetime by using estimates based on annual rates of certain crimes. They estimated that percentage of women who will be raped in their lifetime is estimated to be 8% of women, including 8% of white women and 11% of black women. In fact, people were far more likely to be victims of motor vehicle theft, burglary, robbery, and assault in their lifetime. In fact, the percent raped in their lifetime could be lower now because rape rates plummetted since 1987.

According to Bureau of Justice Statistics for the 2014-15 academic year for college students, the percentage of women who were raped that school year across nine schools were an average of 4.2% if unweighted (4.1% if weighted), and 5.6% were victims of sexual battery that year (this means things like groping and touching and other unwanted sexual contact). Encompassing all forms of sexual assault, 10.3% of college women were sexually assaulted during the 2014-15 year. When it came to unbiased estimates, it was 10.7% and 10.2% for P2 estimates. According to Table 31 and Figure 42, 7.7% of college women were victims of coerced sexual contact in the 2014-15 year, and, according to Figure 43, 5.8% of college men were victims of coerced sexual contact in that year.

Here's another interesting fact: according to Figure 27, sometimes when college women are raped/sexually assaulted, the perpetrator is a non-student/non-professor/non-employee of the school. Perpetrators who were students, professors, or other employees of the school comprised 55% of rape incidents and 56% of sexual battery incident. This means they aren't necessarily part of the school the victim goes to.