After UPenn economist Guido Menzio was taken off a plane last week after a very bright fellow passenger thought the differential equations he was working on were some “terrorist code,” The Economist’s Buttonwood blog published a public service announcement on how people can tell if they’re sitting next to an economist. There are ten items on the list including gems like: “He keeps telling you that ‘there is no such thing’ as a ‘complimentary refreshment service’,” “he plonks his elbow on the arm rest because space has a ‘higher marginal utility’ for him than for you,” and, of course, “he avoids prolonged conversation with you because he has a ‘rational expectation’ that you’re an idiot since you chose the middle seat.”