"That strategic rivalry in a long-term relationship may differ from that of a one-shot game is by now quite a familiar idea. Repeated play allows players to respond to each other’s actions, and so each player must consider the reactions of his opponents in making his decision. The fear of retaliation may thus lead to outcomes that otherwise would not occur. The most dramatic expression of this phenomenon is the celebrated "Folk Theorem." An outcome that Pareto dominates the minimax point is called individually rational. The Folk Theorem asserts that any individually rational outcome can arise as a in infinitely repeated games with sufficiently little discounting."

“It’s true that my initial training was in mathematics. However, almost by accident, I happened to take a course from Kenneth Arrow on “Information Economics,” which was so inspiring that I decided to change direction. It seemed to me that economics combined the best of both worlds: the rigor of mathematics with the immediate relevance of a social science. As for how much math I would recommend, I’d say that basic analysis, including, is certainly very useful. Also, and always helps. But beyond that, I don’t think a huge mathematical investment is necessary to do economic theory unless you are planning to work in an extremely technical area.”

“After society has decided on a social choice rule-a recipe for choosing the optimal social alternative on the basis of individuals' preferences over the set of all social alternatives-the social planner still faces the problem of how to implement that rule. In particular, the planner may not know individuals' preferences. He might attempt to elicit them, but this may not be an easy task, even abstracting from communication costs. If individuals know the rule by which the planner selects alternatives on the basis of reported preferences, they may have an incentive to report falsely.”