In the ultimatum game, there are two players and a sum of money. The first player proposes how to divide up the sum of money, and the second player chooses whether to accept or reject the proposal. If the second player rejects the proposal, neither player receives anything. This game has a unique subgame perfect equilibrium where the first player receives all of the money, or almost all of the money when payoffs are discrete.

Experiments where people have played the ultimatum game have consistently found that the first player will usually offer significantly more money to the other player than the subgame perfect equilibrium, and the second player will be unlikely to accept the offer if they are offered less than 30% of the total amount.[1]

It has been argued by Fehr and Gächter that the ultimatum game provides evidence that economic agents don’t just base their decisions on pure self interest, and reciprocal considerations play an important role in people’s actions. It has been argued by Barrett that the ultimatum game also provides evidence that an international environmental agreement is more likely to be self-reinforcing if it is perceived by its parties to be fair. [2]


[1] Güth et al. (1982), An Experimental Analysis of Ultimatum Bargaining, Journal of Economic Behavior and Organization, 3, pp. 367-388

[2] Fehr and Gächter (2000), Fairness and Retaliation: The Economics of Reciprocity, The Journal of Economic Perspectives, 14 (3), pp. 159-181;  Barrett (2003), Environment and Statecraft – The Strategy of Environmental Treaty-Making, pp. 299-301.

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