When Princeton economist Alan Krueger saw reports that seven of eight people arrested in the unsuccessful car bombings in Britain were doctors, he wasn't shocked. He wasn't even surprised.

"Each time we have one of these attacks and the backgrounds of the attackers are revealed, this should put to rest the myth that terrorists are attacking us because they are desperately poor," he says. "But this misconception doesn't die."

Less than a year after the Sept. 11, 2001, attacks, President Bush said, "We fight against poverty because hope is an answer to terror." A couple of months later, his wife, Laura, said, "Educated children are much more likely to embrace the values that defeat terror." Former World Bank President James Wolfensohn has argued, "The war on terrorism will not be won until we have come to grips with the problem of poverty, and thus the sources of discontent."

The analysis is plausible. It's appealing because it bolsters the case for the worthy goals of fighting poverty and ignorance. But systematic study -- to the extent possible -- suggests it's wrong.

"As a group, terrorists are better educated and from wealthier families than the typical person in the same age group in the societies from which they originate," Mr. Krueger said at the London School of Economics last year in a lecture soon to be published as a book, "What Makes a Terrorist?"