Simple Sequential Equilibria in Generic Extensive-form Games and Forward Induction - Peter Vida

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22

Sep

2026

LEMMA

11h - 12h

Séminaire

Lemma - 4 rue Blaise Desgoffe, 75006 Paris. Salle Maurice Desplas

Péter Vida est professeur à CY Cergy Paris Université et à l'Université Corvinus de Budapest. Ses intérêts de recherche portent sur la microéconomie, la théorie des jeux et le choix social.

Abstract:

Fix a finite extensive-form with perfect recall and a behavioral strategy profile which assigns probabilities to actions in each information set. Assign to each history the number of actions with zero probability. A belief is simple if, at every information set, it assigns positive probability only to histories that minimize this number. I prove that, outside a lower-dimensional semi-algebraic subset of the terminal-payoff space, all games have a simple sequential equilibrium. The proof shows that any uniform epsilon-quasi-perfect equilibrium generically induces a sequential equilibrium with simple beliefs. It follows that essential and Mertens-stable outcomes of a given generic extensive-form game can be supported with consistent simple beliefs. Hence, simple beliefs offer a quick test for stability and essentiality. Coupling forward induction with simple beliefs can be very powerful and testing becomes easier. I discuss the invariance of simple sequential equilibrium outcomes across extensive-form games having the same reduced normal form.

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