One in five women in the United States — more than 23 million in all — have been raped during their lifetimes, and almost half of all women have experienced some other form of sexual violence, such as sexual coercion or unwanted sexual contact, according to a new report released Friday by the Centers for Disease Control and Prevention (CDC).

For men the numbers are much lower, but still troubling: An estimated 1.7 percent of men (almost 2 million) have been raped during their lifetimes, and almost one quarter have been victims of other forms of sexual violence, the report found.

“Although progress has been made in efforts to prevent sexual violence, stalking, and intimate partner violence, these forms of violence continue to exact a substantial toll upon U.S. adults,” the authors of the study write.

The findings are the result of almost 13,000 landline and cell phone interviews conducted by CDC researchers between January and December 2011.

This study adds credence to a 2007 campus sexual assault survey commissioned by the U.S. Department of Justice in which one in five undergraduate women reported being sexually assaulted since entering college. Critics of that study — mostly pundits on the political right — claimed its results were not valid because the survey included only 5,500 women from two colleges.

The CDC study’s finding is also consistent with a UNICEF report published last Thursday that suggests 1 in 10 girls worldwide  — or about 120 million in total — is raped or otherwise sexually abused before age 18.

In the CDC study, 54 percent of the women and 48 percent of the men who had experienced rape or other form of sexual violence said the incident had occurred before they were 25 years old. Among female victims of rape, almost 80 percent said they were first raped before the age of 25, and 40 percent were first raped before the age of 18.

Main findings

Other key findings in the CDC study include the following:

• Sexual violence affects a significant proportion of women of all races and ethnicities. For example, the estimates for women who were raped during their lifetimes broke down like this: 32.3 percent of multiracial women, 27.5 percent of American Indian/Alaska Native women, 21.2 percent of non-Hispanic black women, 20.5 percent of non-Hispanic white women and 13.3 percent of Hispanic women.

• The lifetime estimates of rape for men by race or ethnicity were not statistically reliable, the CDC researchers note, with one exception: an estimated 1.6 percent of non-Hispanic white men were raped during their lifetimes.

• Almost 2 percent of the women surveyed — representing about 1.9 million women — said they had been raped within the previous 12 months.

• The vast majority of rapists are men. Among the people in the survey who had been raped, 99 percent of the women and almost 80 percent of the men said their rapists had been men. Women, however, were often the perpetrators of other forms of sexual violence against men. For example, among the men in the survey who said they had experienced unwanted sexual contact, 54.7 percent said the contact had come from women.

• Most of the victims of sexual violence — men and women — know their perpetrators. Of the people in the CDC study who had been raped, 46.7 percent of the women and 44.9 percent of the men said their rapist was an acquaintance, and 45.4 percent of the women and 29 percent of the men said their rapist was an intimate partner.  

Early prevention needed

This survey has its limitations, of course. Most notably, the response rate was only 33 percent. But those who did participate in the survey were highly cooperative, the CDC researchers point out, and several steps were taken to reduce any bias resulting from people not responding.

“Because a substantial proportion of sexual violence, stalking, and intimate partner violence is experienced at a young age, primary prevention of these forms of violence must begin early,” the CDC researchers conclude.

Prevention needs to focus “on the promotion of healthy relationship behaviors and other protective factors, with the goal of helping adolescents develop these positive behaviors before their first relationships,” they add. “The early promotion of healthy relationships while behaviors are still relatively modifiable makes it more likely that young persons can avoid violence in their relationships.”

The report was published in the Sept. 5 issue of Morbidity and Mortality Weekly Report (MMWR), a CDC publication.