Via all kinds of sources check out this New York Times article about Berkeley math professor David Gale’s arithmetic lesson on averages. Bottom line is that multiple surveys show that the the number of partners reported by men does not add up to the number of partners reported by women. You’d expect a little margin-of-error trouble but not the roughly 75% difference that keeps showing up.

Now much ink is spilled on questions about how this could be — about whether men are misrepresenting themselves (much evidence for this exists), or whether it’s women who are prevaricating (much evidence for this exists), or whether it’s men visiting all those Canadian prostitutes that UK and US researchers overlook (um, some but not very much evidence of this exists, and, again, definitely not enough to explain that 75% gap.)

Professor Gale sidesteps all that.

Dr. Gale added that he is not just being querulous when he raises the question of logical impossibility. The problem, he said, is that when such data are published, with no asterisk next to them saying they can’t be true, they just “reinforce the stereotypes of promiscuous males and chaste females.”

In fact, he added, the survey data themselves may be part of the problem. If asked, a man, believing that he should have a lot of partners, may feel compelled to exaggerate, and a woman, believing that she should have few partners, may minimize her past.

“In this way,” Dr. Gale said, “the false conclusions people draw from these surveys may have a sort of self-fulfilling prophecy.”

Source: New York Times Week In Review: Gina Kolata, Aug. 12, 2007

And that sounds about right to me. If, based on what you hear about other people, your “number” seems higher or lower than average you’re probably going to feel at least some inclination to compare yourself. And depending on what the social stakes are (whichever way you depart from that “norm”) you’re going to be aware of the social consequences whether or not you choose to “correct” our number when asked. We don’t even have to be sexually repressed to fudge our responses (though it certainly doesn’t hurt.)

Anyway, next time the debate about sex-partner reporting disparities comes up think about whether and how (mostly how) previous measurement influences further measurement. And it will keep coming up so long as women are relegated to the “no-sex” class and as long as men relegate ourselves to the “sex class.”