Two years ago, Lara Stemple, Director of UCLA’s Health and Human Rights Law Project, came upon a statistic that surprised her: In incidents of sexual violence reported to the National Crime Victimization Survey, 38 percent of victims were men––a figure much higher than in prior surveys. Intrigued, she began to investigate: Was sexual violence against men more common than previously thought?

The inquiry was a timely one. For years, the FBI definition of rape was gendered, requiring “carnal knowledge of a female forcibly and against her will.” But a recent redefinition focused instead on forced penetration with no mention of gender. Meanwhile, other data-gatherers had started to track a new category of sexual violence that the Centers for Disease Control call “being forced to penetrate.” And still others were keeping better track of sexual violence in prisons.

Taken together, the new data challenged widely held beliefs.

In “When Men Are Raped,” the journalist Hanna Rosin summarized the peer-reviewed results that Stemple published with co-author Ilan Meyer in the American Journal of Public Health. “For some kinds of victimization, men and women have roughly equal experiences,” Rosin wrote. “Stemple is a longtime feminist who fully understands that men have historically used sexual violence to subjugate women and that in most countries they still do. As she sees it, feminism has fought long and hard to fight rape myths—that if a woman gets raped it’s somehow her fault, that she welcomed it in some way. But the same conversation needs to happen for men.”

This awareness-raising need not come at the expense of women victimized by sexual violence, Stemple emphasized to Rosin, because “compassion is not a finite resource.” She also began to wonder, if men were victims of sexual violence far more often than was previously known by researchers, who were the perpetrators? Other men? Women? In what proportions? Under what circumstances?

A new investigation was born.

* * *

Today, the fruits of that research were published in another peer-reviewed paper,  “Sexual Victimization Perpetrated by Women: Federal Data Reveal Surprising Prevalence.” Co-authored with Andrew Flores and Ilan Meyer, it appears in Aggression and Violent Behavior. Once again, federal survey data challenged conventional wisdom.

“These surveys have reached many tens of thousands of people, and each has shown internally consistent results over time,” the authors note. “We therefore believe that this article provides more definitive estimates about the prevalence of female sexual perpetration than has been provided in the literature to date. Taken as a whole, the reports we examine document surprisingly significant prevalence of female-perpetrated sexual victimization, mostly against men and occasionally against women.”

Those conclusions are grounded in striking numbers.

The authors first present what they learned from the The National Intimate Partner and Sexual Violence Survey, an ongoing, nationally representative survey conducted by the Centers for Disease Control and Prevention that measures both lifetime victimization and victimization within the 12 months prior to questioning. Only the 2010 report provides data on the perpetrator’s sex. It found that over their lifetime, women were vastly more likely to experience abuse perpetrated by men, as were male victims who were penetrated without their consent. “But among men reporting other forms of sexual victimization, 68.6% reported female perpetrators,” the paper reports, while among men reporting being made to penetrate, “the form of nonconsensual sex that men are much more likely to experience in their lifetime ... 79.2% of victimized men reported female perpetrators.”

Next they turn to the National Crime Victimization Survey, conducted by the Bureau of Justice Statistics. This survey focuses on violent crime. After pooling and analyzing the data gathered in the years 2010 through 2013, the authors found female perpetrators acting without male co-perpetrators were reported in 28 percent of rape or sexual assault incidents involving male victims and 4.1 percent of incidents with female victims.  Female perpetrator were reported in 34.7 percent of incidents with male victims and 4.2 percent of incidents with female victims.

To study nonconsensual sex among the incarcerated, the authors draw on data collected by the Bureau of Justice Statistics under the Prison Rape Elimination Act. (Their paper focuses on surveys of previously incarcerated inmates in state prisons; Stemple told me that the patterns they related are similar to data collected from those held in a broad range of prisons and jails.) Noting the high prevalence of “sexual victimization committed by female staff members and female inmates,” the authors report that women are “much more likely to be abused” by other women inmates than by male staff.

They add that “for women prisoners and girls in detention, staff perpetrators are overwhelmingly male, and for men and boys the staff perpetrators are overwhelmingly female.” Women are disproportionately represented among all staff abusers because men and boys are so disproportionately incarcerated overall.

Among adults who reported sexual contact with prison staff, including some contact that prisoners call “willing” but that is often coercive and always illegal, 80 percent reported only female perpetrators. Among juveniles, the same figure is 89.3 percent. Queer men and women were two to three times more likely to report abuse. “The disproportionate abuse by female staff members does not occur because women are more often staffing facilities,” the authors write. “Men outnumber women by a ratio of three to one in positions requiring direct contact with inmates.”

Then there’s the finding that surprised me most:

...while it is often assumed that inmate-on-inmate sexual assault comprises men victimizing men, the survey found that women state prisoners were more than three times as likely to experience sexual victimization perpetrated by women inmates (13.7 percent) than were men to be victimized by other male inmates (4.2 percent) (Beck et al., 2013).

The authors also note a 2011 survey of 302 male college students. It found that 51.2 percent reported “at least one sexual victimization experience since age 16.”

About half of the victims reported a female perpetrator.

As well, “a 2014 study of 284 men and boys in college and high school found that 43 percent reported being sexually coerced, with the majority of coercive incidents resulting in unwanted sexual intercourse. Of them, 95 percent reported only female perpetrators. The authors defined sexual coercion broadly, including verbal pressure such as nagging and begging, which, the authors acknowledge, increases prevalence dramatically.”

And “a 2012 study using data from the U. S. Census Bureau’s nationally representative National Epidemiologic Survey on Alcohol and Related Conditions found in a sample of 43,000 adults little difference in the sex of self-reported sexual perpetrators. Of those who affirmed that they had ‘ever forced someone to have sex with you against their will,’ 43.6 percent were female and 56.4 percent  were male.”

Finally, there is reason to fear that abuse by female perpetrators is under-reported:

Tellingly, researchers have found that victims who experience childhood sexual abuse at the hands of both women and men are more reluctant to disclose the victimization perpetrated by women (Sgroi & Sargent, 1993). Indeed the discomfort of reporting child sexual victimization by a female perpetrator can be so acute that a victim may instead inaccurately report that his or her abuser was male (Longdon, 1993).

Male victims may experience pressure to interpret sexual victimization by women in a way more consistent with masculinity ideals, such as the idea that men should relish any available opportunity for sex (Davies & Rogers, 2006). Or, sexual victimization might be reframed as a form of sexual initiation or a rite of passage, to make it seem benign. In some cases, male victims are portrayed as responsible for the abuse. Particularly as male victims move from childhood to adolescence, they are ascribed more blame for encounters with adult women.

And according to the paper, when female abusers are reported, they are less likely to be investigated, arrested, or punished compared to male perpetrators, who are regarded as more harmful.

* * *

The authors completed their research and writeup long before multiple sexual assault allegations roiled the 2016 presidential race. Even so, they were sensitive to the possibility that “a focus on female perpetration might be skeptically viewed as an attempt to upend a women’s rights agenda focused on male-perpetrated sexual victimization.” As they see it, “attention to female perpetration is consistent with feminist approaches that take into account power relations, intersectional analyses, and the imperative to question gender-based stereotypes.”

Stereotypes about women “include the notion that women are nurturing, submissive helpmates to men,” they write. “The idea that women can be sexually manipulative, dominant, and even violent runs counter to these stereotypes. Yet studies have documented female-perpetrated acts that span a wide spectrum of sexual abuse.”

They argue that female perpetration is downplayed among professionals in mental health, social work, public health, and law, with harmful results for male and female victims, in part due to these “stereotypical understandings of women as sexually harmless,” even as ongoing “heterosexism can render lesbian and bisexual victims of female-perpetrated sexual victimization invisible to professionals.”

To date, no existing clinical studies examine large numbers of female sexual perpetrators. As a result, we understand less than we might of a category of sexual perpetrator that, while not the most common, will still victimize many thousands each year.

The authors conclude that in a better world, those charged with responding to sexual victimization would be both gender inclusive, addressing “all victims and perpetrators, regardless of sex,” and gender sensitive, understanding how prevailing norms “influence women and men in disproportionate or different ways.”