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Rabin fairness is a fairness model invented by Matthew Rabin. It goes beyond the standard assumptions in modeling behavior, rationality and self-interest, to incorporate fairness.〔Camerer, Colin & Thaler, Richard H. 2003. "In Honor of Matthew Rabin: Winner of the John Bates Clark Medal." ''Journal of Economic Perspectives.'' 17, 159-176〕 Rabin's fairness model incorporates findings from the fields of economics and psychology fields to provide an alternative utility model. Fairness is one type of social preference. ==Including fairness in the standard utility model== Past utility models incorporated altruism or the fact that people may care not only about their own well-being, but also about the well-being of others. However, evidence indicates that pure altruism does not occur often, contrarily most altruistic behavior demonstrates three facts (as defined by Rabin) and these facts are proven by past events.〔Rabin, Matthew. 1993. "Incorporating Fairness Into Game Theory and Economics." ''The American Economic Review.''83, 1281-1302. 〕 Due to the existence of these three facts, Rabin created a utility function that incorporates fairness.: # People are willing to sacrifice their own material well-being to help those who are being kind. ## The attempt to provide public goods without coercion departs from pure self-interest. ## Experiments show that people cooperate to contribute toward a public good to a degree greater than would be implied by pure self-interest. Individually optimal contribution rates, as defined by the standard utility model, are close to 0 percent. ## During an experiment, the willingness for an individual to contribute to a public good is highly contingent on the behavior of others. # People are willing to sacrifice their own material well-being to punish those who are being unkind. ## Evidence provided by the ultimatum game, consisting of two people, a proposer and decider, splitting a fixed amount of money. The proposer offers a division of the money, then the decider decides if he or she refuses or accepts the proposal. If the decider says yes, they split the money according to the proposer's offer, but if the decider says no, neither person gets any money.〔Thaler, Richard H., "Mental Accounting and Consumer Choice," ''Marketing Science,'' Summer 1985, ''4'', 199-214.〕 ## Standard utility model would find that any offer proposed to the decider should be expected if it is greater than zero because utility should increase with any increase in income. Along the same lines, the standard utility model would predict that the proposer would offer the smallest amount of money possible to the decider in order to maximize his or her own utility ## However, data shows that deciders are willing to punish any unfair offer and proposers tend to make fair offers. # Both motivations 1 and 2 have a greater effect on behavior as the material cost of sacrificing becomes smaller. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Rabin fairness」の詳細全文を読む スポンサード リンク
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