It would be interesting to know if any economists have studied or theorized about tipping. Economists generally assume that the economic behavior of individuals is rational, and that the sum total of individuals' rational economic behavior will be economic efficiency. It seems hard to reconcile these assumptions with tipping. The whole process is wildly irrational and introduces many inefficiencies (bookkeeping, tax avoidance, distortions caused by different assumptions among the people involved about tips, dissatisfaction on both sides of the transactions, to name a few.)

One way to put the question: in areas of the world, e.g. Japan, much of the South Pacific, tipping is not customary. How is the economic functioning of travel and service industries in those places less efficient than in places where tipping prevails? (Maybe should be a separate topic?)