We've long known that blocked upward mobility is a major source of jihadist radicalization, a point that emerged from Sadd Eddin Ibrahim's seminal studies of Egyptian militants in the 1980s. In particular, he found that graduates from rural lower-middle class origins, who had benefited from the expansion of urban post-secondary education opportunities but who were unable to find appropriate job openings and were consequently underemployed (in status and income terms), were especially likely to join Egyptian jihadist groups.

Gambetta and Hertog also point to relative deprivation as an important cause. They might have teased out a bit more here, however, by looking at data on the employment of engineering graduates, the gap between engineers graduated and engineers working as such in the labour force, etc.

They may also be on to something in terms of the impact of disciplinary self-selection and psychological and professional attributes. There is experimental research showing, for example, that when economists play the ultimatum game, they tend to utility maximize (maximize their profits), whereas non-economists put far more emphasis on "fairness" in the division of resources. I've always loved that finding, since it seems to suggest that the only people who behave the way that economists predict are other economists