A Potentially Fruitful Combination: Libertarianism and Economics

It turns out lots of people are thinking and blogging about single motherhood and the sexual revolution. Apparently Santorum said that if elected, he would be the first President to talk about the "dangers of contraception." He elaborated:

"What I was talking about is we have a society -- Charles Murray just wrote a book about this and it's on the front page of 'The New York Times' two days ago, which is the increasing number of children being born out of wedlock in America, teens who are sexually active."

Julian Sanchez, who works for Cato and is a contributing editor to Reason magazine, had this response:

"On its face, this is nonsensical: How can contraception, of all things, be responsible for an increase in out of wedlock births?"

Sanchez goes on to spin an elaborate story about how social conservatives are playing a Straussian game of hide-the-ball when they talk about how people play hide-the-banana, deliberately avoiding discussion of differences between elites and non-elites. Ross Douthat argues that Sanchez is simply mistaken and that conservatives aren't hiding anything - they openly discuss differences between elites and non-elites when it comes to sex (as well as other issues such as gambling).

I suspect Douthat is right, but what baffles me here is Sanchez's conceit that it is nonsensical for contraception to be responsible for an increase in out-of-wedlock births (he goes so far as to state that his Straussian explanation is "the only remotely coherent way I can see to make sense of Santorum’s purported link between the prevalence of contraception and rising non-marital births"). The thing is, Santorum's claim is actually perfectly plausible without resort to tortured explanations. A fairly simple model should suffice:

1. The casual sex market is greatly facilitated by contraception, which is generally effective not only to prevent pregnancy but also to reduce transmission of disease (I am thinking of condoms - obviously the pill is not effective against disease). Contraception "lowers the cost" of casual sex (not the monetary cost, but the overall consequences).

2. Pregnancy is less likely to result from each sexual encounter. Total pregnancies among single women are probably reduced by contraception (though pregnancies could theoretically increase if the number of sexual encounters were to grow substantially - but I think we can ignore this possibility).

3. At the same time, because casual sex is easier to obtain, men will have less incentive to commit to long-term committed relationships. The "supply" of marriageable men is reduced.

4. So the net effect on single motherhood will depend (roughly) on whether #2 or #3 predominates - whether out-of-wedlock pregnancies will fall more or less than the "supply" of husbands.

Far from being incoherent, Santorum's account is actually quite logical. He is advancing the claim that #3 predominates - that casual sex, facilitated by contraception, is drawing men away from marriage and leaving unwed mothers with few good options.

[Update: Note that as with the sexual revolution, I support access to contraception despite its potentially negative consequences for some people. I am an enthusiastic user of birth control, although my method happens to consist of my personality and appearance.]

As a general matter, I would encourage people who are interested in libertarianism (as I assume Sanchez is) to study basic economics and to consider incentives when thinking about human behavior. Although it's true that an understanding of economics often undermines libertarianism, a general facility with basic economics would help libertarians think through their arguments. And sometimes economics actually provides support for libertarian arguments - a win-win.