Justin Lahart has a great piece in the Wall Street Journal chronicling stories of economists who practice what they preach by acting “rationally” — maximizing personal utility. For instance, John Sigfried, a professor at Vanderbilt, bought a black car instead of a gray one, even though he preferred gray, because it was $100 cheaper. Robert Hall, a Stanford professor, wants to hire someone to trim his Christmas tree so he can use the time for more productive things.

Economists typically posit that people act in their own interest — they maximize their own utility, or happiness. It explains why studies have shown that economists free ride — get others to pay for things from whcich they themselves benefit — and contribute less to charity. A purely self-interested person would never give to charity; yet people give to charities all the time.

All of which give rise to the question: are economists cheap because they assume people are self-interested, or do self-interested people gravitate to studying economics?