Putting Incest to the TestBetween Eugene (see links in post below) and Amy, the defense of legalizing consensual incest is pretty much complete. But I want to raise one more question, of the sort that economists are apt to raise: what is the elasticity of incestuous acts with respect to criminal punishment? My strong suspicion is that it’s damn near zero. It’s hard for me to imagine that a large number of people are just waiting for the chance to nail their siblings -- and are being deterred on the margin by the existence of a law against it. If I’m correct, then resources spent on prosecuting and punishing those who commit consensual incest are mostly wasted from the standpoint of deterrence, even if you agree that it’s the state’s job to deter such things.
A similar observation applies to bestiality. How many folks would not currently do a sheep, but would suddenly give it a try if the law changed? Again, I’ll bet the number is just about zero. I suspect that basically everyone who leans that way, and who has access to a sheep, is doing it already.
Of course, the folks who support laws to enforce their own sexual preferences probably don’t agree that deterrence is the main purpose of the law. They like to pass laws purely for the “message” value. But unless that message actually prevents some acts of incest *on the margin* (no fair counting acts of incest that will be deterred by social disapproval, regardless of law), then I just don’t see the point.