John McCain apparently had an awkward exchange with reporters today when one asked whether he thought it was fair that insurance often covers Viagra but not birth control pills. Obviously there’s a superficial symmetry, but I’d think the distinction is pretty elementary: Erectile disfunction is, in theory, a medical condition that will unpredictably strike some and not others; fertility is not. In the former case, there’s some argument to be made for risk pooling, as with other unpredictable medical afflictions. In the latter case, except when the pill is being used as treatment for some such condition, there’s not. Birth control is just a wholly predictable regular expense for most people who want to have sex without babies. Having insurance cover it doesn’t actually pool any risk, it just shifts part of the cost from people who choose to use it to those who don’t.

Think of it this way: Imagine you let people choose in advance between a plan that covers birth control and a plan that doesn’t. The only people who elect the plan that covers it are those who expect to use it regularly, at which point everyone’s still essentially paying the cost of their own pills, but in their premium rather than at the counter. The only way it actually gets covered, then, is if you eliminate the choice and require those who don’t use birth control to subsidize those who do. But if you think that’s the way things ought to be, why bother with the insurance middleman? Why not just say that every woman is entitled to a supply of free, publicly-funded birth control, and have done with it?

There is one way I can think of to make a risk-pooling argument work, which is this. If insurance covers maternity costs, if a significant number of people will just go without birth control if it’s not covered, if some of them will become pregnant who otherwise wouldn’t, and if the cost of covering the additional pregnancies exceeds the cost of covering birth control, then it might make sense from an actuarial standpoint. I have my doubts, but that’s an empirical question, and it at least seems possible.

All that said, part of the reason the differential treatment of birth control and Viagra might nevertheless seem intuitively unfair is that we know in practice there are plenty of people using the little blue pill as an elective performance enhancer.  And in those cases, the analogy does work well enough. In a sense, then, the disconnect between the cases is a function of our uneasiness with the idea of better living through chemistry. So instead of saying that as men get older, we stop walking around with constant erections, we class any gap between our ideal and actual performance as Erectile Dysfunction, even though it’s arguably as predictable a consequence of aging as fertility (and, later, infertility).