Nearly one of every 10 American teenagers has committed rape or sexual assault, according to a new pediatrics study.

In researching a poorly understood area of sociology, investigators from the University of New Hampshire at Durham and colleagues from California analyzed data from more than 1,000 American youngsters 14 years of age to 21, finding sexual violence to be fairly prevalent among American youth.

Some 9 percent of young Americans acknowledged perpetrating some type of sexual violence against another, including rape and coerced sex. Four percent of young Americans say they’ve either raped or attempted to rape someone, with 40 percent of perpetrators committing such an act at the age of 16. At younger ages, boys were far more likely to commit sexual violence than girls, though boys and girls committed such offenses at more or less equal rates by the age of 18 and 19, at 52 percent to 48 percent, respectively.

Aside from an earlier age of sexual transgressions among boys, researchers found a higher prevalence of sexual violence among white kids and those from upper-middle class backgrounds.

In the breakdown, 8 percent of those studied said they had forced sexual acts—kissing, groping—on someone else, with 3 percent verbally coercing another into sex. Another 3 percent attempted rape with physical force, and 2 percent committed rape.

“Sexual violence perpetration appears to emerge earlier for males than females, perhaps suggesting different developmental trajectories,” the researchers wrote in a study published Monday. “Links between perpetration and violent sexual media are apparent, suggesting a need to monitor adolescents’ consumption of this material.”

The researchers noted that teenagers who’d viewed violent pornography were more likely to commit a violent sexual act, with non-violent pornography making no difference.

The study also found victim-blaming to be common among youthful perpetrators of sexual violence, with half blaming the victim and just over a third blaming themselves.

Writing in Slate, feminist Amanda Hess says the study “challenges popular assumptions about teen sexual violence,” noting that girls can be perpetrators and boys victims. The study authors also suggest researchers and policy makers reassess long-held assumptions about a greater prevalence of such acts occurring within underprivileged populations, and encourage the development of school programs intended to lower the rate of sexual violence among American adolescents and teenagers.

Source: Ybarra, Michele L., Mitchell, Kimberly J. Prevalence Rates Of Male And Female Sexual Violence Perpetrators In A National Sample Of Adolescents. JAMA Pediatrics. 2013.