In fact, there is now robust evidence that there is no such link. That does not mean, however, that economics is irrelevant.
First, to the question of poverty. Of the 50 poorest countries in the world only Afghanistan (and perhaps Bangladesh and Yemen) has much experience in terrorism, global or domestic.
But surely that is the wrong way to look at things. Aren't the people who commit terrorist acts poor, even if they are from countries that are not? No. Remember, most of the 19 hijackers on 9/11 were middle-class sons of Saudi Arabia and many were well-educated. And Osama bin Laden himself is from one of the richest families in the Middle East.
But it goes deeper than that. In a 2003 study in the Journal of Economic Perspectives, Alan Krueger and Jitka Maleckova reported the results of a post-9/11 survey of Palestinians. Asked whether there were "any circumstances under which you would justify the use of terrorism to achieve political goals," the higher-status respondents (merchant, farmer or professional) were more likely to agree (43.3 percent) than those lower down the ladder (laborer, craftsman or employee) (34.6 percent).
The higher-status respondents were also more likely to support armed attacks against Israeli targets (86.7 percent to 80.8 percent). The same dynamic existed when education was taken into account.