Economics of Spongeworthiness: An Option Value Problem

A Princeton economist has devised a formula for a classic sitcom paradox.

Princeton economist Avinash Dixit has, after years of postponing doing so for fear of being dubbed “politically incorrect,” has published [PDF] an econometric formula to calculate “spongeworthiness.”

Suppose Elaine believes herself to be in finitely lived; this is a good approximation in relation to the number of sponges she has and her time-discount factor or impatience. She meets a new man every day. De fine the quality Q of each man as Elaine’s utility from having sex with him. This is independently and identically distributed, and drawn each day from a distribution which I assume to be uniform over [0,1]. Each day she observes the Q of that day’s date. Actually this is only her estimate formed from observing and closely questioning the man (which is what she does in the episode), not the ex post facto outcome. But I assume that she has sufficient experience and expertise to make a very accurate estimate. Having observed Q, she makes her yes/no decision. Elaine’s per-day discount factor is β .  All these assumptions are to simplify the calculations; the method is perfectly general and many bells and whistles can be added to the analysis.

The formula he comes up with takes up several pages.

This demonstrates at least three things.

First, this Dixit fellow really has too much time on his hands.

Second, there really is economics in everything.

Third, human decisionmaking is enormously complex yet often seems quite simple.  The Elaine character isn’t particularly bright, yet she intuitively understands marginal utility and weighs numerous variables almost instantaneously.

via Tyler Cowen

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James Joyner
About James Joyner
James Joyner is Professor and Department Head of Security Studies at Marine Corps University's Command and Staff College. He's a former Army officer and Desert Storm veteran. Views expressed here are his own. Follow James on Twitter @DrJJoyner.


  1. steve says:

    Dixit failed to add in the alcohol consumption factor which I suspect is key in many of these kinds of decisions. It used to make me much more spongeworthy.

    I think we can get a pretty good handle on rational decision making. It is the irrational which eludes us, along with deciding what is rational and is not. Too many of our assumptions about macro assume rationality where it does not exist.


  2. sam says:

    “Dixit failed to add in the alcohol consumption factor which I suspect is key in many of these kinds of decisions. It used to make me much more spongeworthy.”


  3. Brummagem Joe says:

    C’mon Jim surely Dixit is allowed a little whimsy, even Einstein used to construct humorous theorems. But you’re surely right about the other two. It’s complex and economic considerations are always present.