# Chaste women + promiscuous men = impossible

## Mathematicians take on surveys finding gap between men's and women's number of sex partners.

### Published August 13, 2007 7:25PM (EDT)

I never thought I'd be so happy to see mathematicians take on the subject of sex in an entirely sober and unsexy way. But -- hallelujah! -- some left-brained number crunchers have taken on the staggering discrepancy between the median number of sex partners heterosexual men and women have been shown to have in survey after survey.

Just last month, a survey released by the National Center for Health Statistics reported that men had a median of seven sex partners, while women had a median of four. That finding left plenty of women feeling ... statistically slutty. But as the New York Times reports, David Gale, professor emeritus of mathematics at the University of California at Berkeley, is sounding the logic alarm, suggesting that the results are mathematically impossible. "Surveys and studies to the contrary notwithstanding, the conclusion that men have substantially more sex partners than women is not and cannot be true for purely logical reasons," he said.

In true mathematician form, he offered the New York Times a proof via e-mail:

By way of dramatization, we change the context slightly and will prove what will be called the High School Prom Theorem. We suppose that on the day after the prom, each girl is asked to give the number of boys she danced with. These numbers are then added up giving a number G. The same information is then obtained from the boys, giving a number B.

Theorem: G=B

Proof: Both G and B are equal to C, the number of couples who danced together at the prom. Q.E.D.

For the mathematically challenged, the Times put it this way: "Men and women in a population must have roughly equal numbers of partners." The thing is, though, researchers behind these many sex surveys that confirm what we know to be true -- men are promiscuous and women are stringently close-legged -- say they've long known that the findings don't make sense. Yet they publish them anyway without noting the impossibility of their findings.

Researchers have proposed a couple of explanations for the seemingly nonsensical stats. For one, "men are going outside the population to find partners, to prostitutes, for example, who are not part of the survey, or are having sex when they travel to other countries." Gale doesn't buy it, though; he says the effect of "outsider" sex "would be negligible" and couldn't account for such a yawning gap. Another, more believable hypothesis is that men are culturally motivated to overstate their number of sex partners to underline their manhood: "Some might be imaginary," Ronald Graham, professor of mathematics at the University of California at San Diego, told the Times. "Maybe two are in the man's mind and one really exists." It's also not so hard to believe that women, on the other hand, might have plenty of motivations to underestimate their "number."

The article's true hallelujah moment comes when Gale tosses aside his theorems and proofs and argues that publishing these fishy findings reinforces "the stereotypes of promiscuous males and chaste females." He continues: "In this way, the false conclusions people draw from these surveys may have a sort of self-fulfilling prophecy."

Update: Since so many folks wrote into our letters thread taking issue with the fact that professor Gale commented that the average number of sexual partners needs to be the same while the actual survey reports the median number of partners, I shot him an e-mail, giving him a chance to respond. Here's what he said:

I've gotten several messages making the same point. If you look at Gina's article you will see that I never attacked the statement about medians. I tried to carefully avoid saying anything directly about the median statement in the article because, as you realize, it could be correct even with accurate data. What I did was to get a copy of the CDC report and used the data in its tables. It groups people into four groups and gives the percentage of men and women in each group:

0-1 partner: Men, 16.6. Women, 25.0.
2-6 partners: Men, 33.8. Women, 44.3.
7-14 partners: Men, 20.7. Women, 21.3.
15 or more partners: Men, 28.9. Women, 9.4.

From these figures you can estimate the total partners claimed by each sex. I got between 40 percent and 75 percent more male than female partners depending on how you guess the average on each interval. Thus, the raw data is inconsistent (so it doesn't matter whether you take averages or medians or any other statistic). I hope this clarifies.

### By Tracy Clark-Flory

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