“Nash’s major contribution is the concept of equilibrium for noncooperative games, which later came to be called a Nash equilibrium. A Nash equilibrium is a situation in which no player, taking the other players’ strategies as given, can improve his position by choosing an alternative strategy. Nash proved that, for a very broad class of games of any number of players, at least one equilibrium exists as long as mixed strategies are allowed. A mixed strategy is one in which the player does not take one action with certainty but, instead, has a range of actions he might take, each with a positive probability.

A simple example of a Nash equilibrium is the prisoners’ dilemma. Another example is the location problem. Imagine that Budweiser and Miller are trying to decide where to place their beer stands on a beach that is perfectly straight. Assume also that sunbathers are located an equal distance from each other and that they want to minimize the distance they walk to get a beer. Where, then, should Bud locate if Miller has not yet chosen its location? If Bud locates one-quarter of the way along the beach, then Miller can locate next to Bud and have three-quarters of the market. Bud knows this and thus concludes that the best location is right in the middle of the beach. Miller locates just slightly to one side or the other. Neither Bud nor Miller can improve its position by choosing an alternate location. This is a Nash equilibrium.

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