According to survey data released yesterday by the CDC, "nearly 1 in 5 women" in the United States "have been raped at some point in their lives." If that figure seems surprisingly high, it might be partly because the definition of rape used by the National Intimate Partner and Sexual Violence Survey includes "alcohol/drug facilitated completed penetration."

The relevant question asked: ""When you were drunk, high, drugged, or passed out and unable to consent, how many people ever" "had vaginal sex with you," "made you receive anal sex," or "made you perform oral sex." Eight percent of women reported at least one such incident. Some of these cases—e.g., when a man has sex with a woman who is unconscious—clearly do amount to rape, but others are much more ambiguous. People frequently have sex after drinking or consuming other drugs. Does that automatically mean they are "unable to consent," even when they seem willing? Only sometimes? How do you know when? Can the determination be made at the time of the encounter, or only in restrospect? Such a standard would implicate many men in crimes they did not realize they were committing. Furthermore, the way people behave under the influence of alcohol or other drugs is strongly influenced by their expectations. Drugs may impair judgment, but they may also be a license and an excuse. The question about "alcohol/drug facilitated completed penetration" seems like an invitation to shift responsibility for regrettable sexual encounters.

The widely cited "1 in 5" figure (18.3 percent, to be precise) also includes "attempted forced penetration," which was reported by 5.2 percent of women. Since the question for such incidents refers to "physical force or threats of physical harm," these are much more clearly criminal assaults, but still not what most people imagine when they hear that a woman has been raped. Attempted murder and murder are both crimes, but they are not the same crime.

The share of women reporting "forced completed penetration" (meaning sex involving "physical force or threats to physically harm you") was 12.3 percent—still pretty appalling, but one-third lower than the number making headlines. Isn't "more than 1 in 10" bad enough?

The numbers from the CDC survey are far higher than those reported by the Justice Department's National Crime Victimization Survey, which in 2010 found an annual risk of rape or sexual assault of 1.3 per 1,000 females 12 or older, or 0.13 percent. In the CDC study, by contrast, 1 percent of women 18 or older "reported some type of rape victimization in the 12 months prior to taking the survey." That rate is nearly eight times as high—a huge gap, even allowing for the difference in the ages of the respondents. While the CDC survey counts 1.3 million rapes of women in 2010, the total number of rapes and sexual assaults (of males and females combined) in the Justice Department survey was 188,380.

In an NRO post, Robert VerBruggen suggests the Justice Department's survey is more reliable because it has a much bigger sample and a much higher response rate. Another important difference may be the wording of the relevant question:

Has anyone attacked or threatened you in any of these ways (exclude telephone threats) (a) With any weapon, for instance, a gun or knife (b) With anything like a baseball bat, frying pan, scissors, or stick (c) By something thrown, such as a rock or bottle (d) Include any grabbing, punching, or choking, (e) Any rape, attempted rape or other type of sexual attack (f) Any face to face threats OR (g) Any attack or threat or use of force by anyoneat all? Please mention it even if you are not certain it was a crime.

Despite that last caveat, the context of the question invites respondents to focus on criminal acts, whereas the CDC survey takes (and invites) a broader view of what counts as rape.