Dominantstrategy

Dominantstrategy is a concept in game theory that refers to a strategy which yields a higher payoff for a player regardless of the strategies chosen by the other players. When a dominant strategy exists, it is considered rational for the player to adopt it, because no other strategy can give a higher payoff in any scenario. The strategy can be either strictly dominant, meaning it always leads to a strictly better payoff, or weakly dominant, meaning it is at least as good in all cases and better in at least one.

In a strategic form game, player i’s strategy s_i is dominant if for every possible combination of opponents’ strategies s_-i, u_i(s_i, s_-i) ≥ u_i(s_i', s_-i) for all alternative strategies s_i'. A game that has a dominant strategy for each player is called a dominant strategy equilibrium.

Common examples include the Prisoner’s Dilemma, where defection is a strictly dominant strategy for both players, and certain auctions where bidding one's true valuation is a dominant strategy. The concept is distinct from other solution concepts such as Nash equilibrium or subgame perfect equilibrium, where multiple equilibria or contingent strategies may arise.

Dominantstrategy analysis is often used in mechanism design, contract theory, and behavioral economics to predict outcomes in settings such as market auctions, voting, and public goods provision. The existence of a dominant strategy assures predictability and simplifies the strategic reasoning required from participants.