ECON 159: Game Theory. Lecture 19 - Subgame Perfect Equilibrium: Matchmaking and Strategic Investments Overview. Not all NE are SPNE. Game Theory Chris Georges Some Notation and Deï¬nitions 1. In game theory, the centipede game, first introduced by Robert Rosenthal in 1981, is an extensive form game in which two players take turns choosing either to take a slightly larger share of an increasing pot, or to pass the pot to the other player. For ï¬nite games of perfect information, any backward induction solution is a SPNE and vice-versa. The whole game. Mark Voorneveld Game theory SF2972, Extensive form games 18/25. This game has 3 subgames: The game 2 plays if 1 plays A. stated in the beginning of the class implies that there is a unique SPNE in the ï¬nite repetition of this game, namely in each and every stage. In game theory, a subgame perfect equilibrium (or subgame perfect Nash equilibrium) is a refinement of a Nash equilibrium used in dynamic games.A strategy profile is a subgame perfect equilibrium if it represents a Nash equilibrium of every subgame of the original game. Consider the strategies: 1:play nc in every stage â¢ Since the whole game is always a subgame, every SPNE is a Nash equilibrium, we thus say that SPNE is a reï¬nement of Nash equilibrium â¢ Simultaneous move games have no proper subgames and thus every Nash equilibrium is subgame perfect â¢ SPNE can be found using a simple algorithm known as backward induction (cf Zermelo 1913) The ad-vantage of SPNE is that it can be applied to games of imperfect information too. The game 1 plays if 1 plays B. We analyze three games using our new solution concept, subgame perfect equilibrium (SPE). theory. Notice that every SPNE must also be a NE, because the full game is also a subgame. This remains an SPNE outcome of the inï¬nitely repeated game. Dynamic Game Theory Equilibrium concept Some NEs are odd in the dynamic context â¢ so thereâs a need to refine equilibrium concept Introduce Subgame -Perfect Nash Equilibrium (SPNE) A profile of strategies is a SPNE for a game if it â¢ is a NE â¢ induces actions consistent with NE in every subgame April 2018 24 To find the Subgame Perfect Nash equilibrium, we need to solve for the nash equilibria of each subgame. At a NE that is not a SPNE, some player is playing a strategy that is a BR in ... game (of complete information) must have at least one SPNE. A is a best response if and only if the player assigns at most prob 1=2 In the subgame identified in 2, \$(E,X)\$ is the unique nash equilibrium. In the subgame identified in 1, player 2 plays C, because \$4>2\$. Beliefs and optimal strategies a ecting each other The following game has no proper subgames: Beliefs a ect optimal strategies:consider pl 2 in info set fM;Rg. 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