More Sex is Safer Sex

I had forgotten that Steven Landsburg’s More Sex is Safer Sex (link to the 1997 NYTimes version, book here) was inspired by a paper by new Nobelist Michael Kremer. Here’s the recap:

You’ve read elsewhere about the sin of promiscuity. Let me tell you about the sin of self-restraint.

Consider Martin, a charming and generally prudent young man with a limited sexual history, who has been gently flirting with his coworker Joan. As last week’s office party approached, both Joan and Martin silently and separately entertained the prospect that they just might be going home together. Unfortunately, Fate, through its agents at the Centers for Disease Control, intervened. The morning of the party, Martin happened to notice one of those CDC-sponsored subway ads touting the virtues of abstinence. Chastened, he decided to stay home. In Martin’s absence, Joan hooked up with the equally charming but considerably less prudent Maxwell – and Joan got AIDS.

When the cautious Martin withdraws from the mating game, he makes it easier for the reckless Maxwell to prey on the hapless Joan. If those subway ads are more effective against Martin than against Maxwell, they are a threat to Joan’s safety. This is especially so when they displace Calvin Klein ads, which might have put Martin in a more socially beneficent mood.

If the Martins of the world would loosen up a little, we could slow the spread of AIDS. Of course, we wouldn’t want to push this too far: if Martin loosens up too much, he becomes as dangerous as Maxwell. But when sexual conservatives increase their activity by moderate amounts, they do the rest of us a lot of good. Harvard professor Michael Kremer estimates that the spread of AIDS in England could plausibly be retarded if everyone with fewer than about 2.25 partners per year were to take additional partners more frequently.

And here is Kremer’s original paper (with Charles Morcom). Landsburg suggests that a subsidy for condoms would be optimal in this situation. Read the whole thing.

Addendum: I later pointed out that the Kremer model appears to fit what happened in Thailand quite well.