In 2015, 10% of female college students experienced some form of sexual assault, according to a major new survey of 23,000 undergraduates.

The survey is a result of the 2014 White House Task Force to Protect Students from Sexual Assault, which reported a need for more data on campus sexual assaults.

The Bureau of Justice Statistics interviewed students from nine colleges across the country, asking for the details of specific sexual assaults that had occurred during the 2014-2015 school year.

The agency found that 4% of students had been raped during that academic year, and more than 5% had encountered sexual battery, including unwanted kissing or forced touching.

The numbers of reported assaults varied widely depending on the schools, which were unnamed in the survey, but were chosen specifically to represent a mix of small and large, public and private colleges across the country.

The rate of sexual assault at the “worst” school (20%) was five times greater than at the “best” (4%). The prevalence of rape ranged from 2% at one school to nearly 8% at another.

Advocates said the disparate range indicates that certain colleges foster toxic environments.

“This demonstrates that rape isn’t a normal part of the college experience, but rather a horror that can be prevented with strong action from campus leadership and by holding more perpetrators accountable,” said Scott Berkowitz, president and founder of the Rape, Abuse and Incest National Network (Rainn), an advocacy group for victims of sexual assault.

Although the colleges from the survey are unknown, Sofie Karasek, director of education at End Rape on Campus, noted that there are two recurring factors in colleges with higher incidents of sexual assault: sports and fraternities.

Statistics have shown that 20% of campus sexual assault perpetrators are athletes, she said, noting that members of fraternities are three times more likely to commit sexual assault.

“Unfortunately there’s a culture of sexual assault that exists in both of these spheres. There’s often a level of impunity given to both of these organizations,” Karasek said.

“Schools that don’t have a big athletic culture or a big Greek life have fewer incidents of sexual assault,” she said.

When announcing the sexual assault taskforce in January 2014, Obama noted that one in five women are sexually assaulted during their time at university.

The new BJS survey has backed up that commonly-touted statistic, finding that on average, one in five female respondents had experienced an incident of sexual assault since beginning college.

Further, only 12.5% of the surveyed rapes were ever officially reported, which could include telling a police officer, college official or hospital official. Just 4.3% of sexual battery incidents were reported.

Karasek said these low numbers of reporting sexual assaults are pretty standard for campus sexual assault.

“A big part of the reason why that is is that people don’t expect that the people they are reporting it to will do anything about it,” she said.

Rapists are most likely to be men (94%) and known to the victim (59%), according to the survey. Victims are most likely to be women age 18-22. But the survey also showed higher numbers of sexual assaults reported by non-heterosexual women.

Approximately 15,000 women and 8,000 men responded to the survey, with the full results published in a 425-page report.