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Subgame Perfect

Definition

Subgame perfect is a refinement of Nash equilibrium used in extensive-form games, where players make sequential decisions. An equilibrium is subgame perfect if the players’ strategies constitute a Nash equilibrium in every subgame of the original game. This concept ensures that strategies remain optimal at every stage of the game, even if previous moves deviated from the equilibrium path. It rules out non-credible threats and promises, providing a more robust prediction of rational behavior.