Sex math

A controversy has been simmering at the NY Times over how many sex partners men and women have, on average. Dr. David Gale (a famous Berkeley mathematician) is disturbed by what he believes is inconsistent data collected in numerous sex surveys worldwide. On average, men typically report more sexual partners than women. Dr. Gale argues that the means must be exactly the same, because it represents to mean number of pairings. If you multiply the number of females times their average number of sex partners, you get (approximately) the total number of sexual pairs. The number of heterosexual pairs has to be the same for both sexes. The problem is that surveys consistently find that men report as much as 75% more pairings than women. Men are somehow finding sex partners who are not finding them back.

This argument is interesting and straightforward, but when it was originally reported in the NY Times, it sparked a wild controversy over the soundness of Dr. Gale's math. The controversy was sparked when the Times article cited a difference in median sex partners for one study:

One survey, recently reported by the federal government, concluded that men had a median of seven female sex partners. Women had a median of four male sex partners. Another study, by British researchers, stated that men had 12.7 heterosexual partners in their lifetimes and women had 6.5.

As soon as this article printed, math enthusiasts pounced. The averages should be roughly equal, not the medians. This mistake was apparently reported in every imaginable media outlet, and was held as a humiliation not only for the NY Times, but for Dr. Gale himself. But Dr. Gale was correct, and his analysis does reveal problems with the medians as well as the means. By condensing his argument in a mathematically sloppy fashion, the NY Times dissolved his point and exposed him to ridicule.

This makes a somewhat interesting case study for my "rumor-mill" model of the popular news media. Somewhere in the reporting and editing process, Dr. Gale's sound scientific point got dissolved. As other outlets "picked up" the story, its theme transformed from "sex data is wrong" to "famous mathematician makes embarrassing mistake." The Times ultimately ran another article that cleared things up a bit, but it is not likely that the clarification will reach as many ears as the guffaw.

I believe that this demonstrates a fundamental flaw in how newspapers and magazines report science news. The process is almost entirely feed-forward. Shannon's Data Processing Lemma dictates that you can only lose information with each step of rewording a story. Blog news sites, like Slashdot, are much more successful at reporting news stories because they are so often able to link directly to a story's source, and because persons with inside knowledge routinely contribute supplemental or correcting information to a story's comments thread. There's no perfect recipe for making this happen, but I do suspect that Wiki-style news should emerge as a preferred means of delivering information to the public. I say "should" not as a prediction, but more as a moral judgement. Better methods should win. Newspapers should die.