## Tuesday, May 10, 2005

### Doing It With Models

Tyler Cowen addresses the question, “Why don’t people have more sex?” Tyler offers a possible explanation (#2 of 12):
The average utility of sex is high but the marginal utilities are falling off a cliff. You just don't want any more. But how many people are at this margin?
If people enjoy sex as much as they say, it seems like they should always have more sex if the added pleasure of one more sex act is greater than the added cost. That’s basic cost-benefit analysis, right? But as I’ve argued before, it’s not necessarily true.

The key point is that the value of all acts of sex, not just the marginal act, may decline as the number of acts increases. Here’s how I put it before (yes, I’m actually quoting myself): “As the frequency of sex acts increases, it’s not just that each act is less satisfying than the previous one, it’s that the satisfaction from each and every act may decline. For instance, a person who has sex twice a week may appreciate each instance more (because of greater anticipation, built-up sexual tension, and so on) than a person who has sex every day.” As a result, the marginal utility of an act of sex is lower than the utility derived from your most recent sex act.

Suppose Phyllis is contemplating an increase in her sex frequency from thrice to four times per week. She finds that the fourth sex act, considered in isolation, will generate net satisfaction: the pleasure gained will be greater than the opportunity cost of not watching TV or getting another hour of sleep. Nonetheless, she rationally chooses not to increase her sex frequency. Why? Because if she has sex four times a week, every act will be less satisfying than it would otherwise be. Once that reduction in satisfaction for the first three acts per week is subtracted from the new satisfaction attributable to the fourth, the benefits no longer justify the costs. CSI: Dubuque it is.

Loquitur Veritatem said...

Here's my hypothesis: The marginal enjoyment of sex actually increases with frequency, up to a fairly high rate (e.g., 7 times a week), which varies by individual. The problem is that for working parents (especially) the opportunity cost of sex begins to outweigh the marginal enjoyment of sex at a sex-frequency lower than that at which marginal enjoyment peaks. Why? Good sex -- which takes time -- competes with sleep, with work, with caring for children, etc. So, it's not necessarily about the diminishing marginal utility of sex, it's about the opportunity cost of sex. As a result, most persons find that the break-even point (enjoyment of sex = enjoyment/duty in other aspects of life) comes before the marginal utility of sex peaks. The result: frustration and a thousand other ills that flesh is heir to. Too little sex is socially disruptive and unhealthy. But we nevertheless honor our non-sexual commitments, to the detriment of social harmony.

Will Wilkinson said...

You think that the economics of sex is interesting? NO! But the idea CSI: Dubuque is riveting to this Iowan. I see that in 2002, Dubuque had a murder.

http://dubuque.areaconnect.com/crime1.htm

I wonder if they've solved it!? Do they need CSI in Dubuque? That's what I want to know.

Anonymous said...

Glen, this is so sad. Perhaps you have not found the right gal who can change this equation. 'Tis very discouraging to read all of these thoughtful men* write about diminishing sexual returns.
*the men who comment at Cowen's Wilkinson's and your sites.

gt said...

Sex has costs and risks.
Three times recently I've turned down sex. a) was a crack whore. b) was my roommate's girlfriend. c) would have gotten us thrown out of the bar, plus the relationship is at an awkward stage.
My aversion to sex, and social interaction in general, kept me alive through the plague years when many of my friends died.
As Marx said, I wouldn't want to join a club that would have me as a member.
Sex comes in two flavors, impersonal and personal.
The costs of personal sex are that she will expect you to listen to her complain about stuff, and maybe help raise the children. Maybe her views on abortion aren't compatible with yours. Maybe she, or you, has some new as-yet undiagnosed communicable disaease.
From each as he chooses, to each as he is chosen. You may be overestimating how eager women are to have sex with me.
And it's not that i mind guys, but the dynamic there is I and they want to have sex with prettier, younger guys. I could probably be having more sex with fat old guys if I wanted.
If I spent more, I could probably have more sex, but that would involve other trade offs.
Internet porn is a substitute good with high utility; I wouldn't want to spend the cable bill on a hooker.
I could go on, but that's the idea.
Risks and costs.