• Jeff Ely

Critical Types

Joint with Marcin Peski


How can we know in advance whether simplifying assumptions about beliefs will make a difference in the conclusions of game-theoretic models? We define critical types to be types whose rationalizable correspondence is sensitive to assumptions about arbitrarily high-order beliefs. We show that a type is critical if and only if it exhibits common belief in some non-trivial event. We use this characterization to show that all types in commonly used type spaces are critical. On the other hand, we show that regular types (types that are not critical) are generic, although perhaps inconvenient to use in applications.


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Jeffrey Ely

Department of Economics

Northwestern University

2211 Campus Dr Evanston, IL 60208

Curriculum Vitae

©2019 by Jeffrey Ely.