Ex post implementation

Dirk Bergemann, Stephen Morris

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


We analyze the problem of fully implementing a social choice set in ex post equilibrium. We identify an ex post monotonicity condition that is necessary and-in economic environments-sufficient for full implementation in ex post equilibrium. We also identify an ex post monotonicity no veto condition that is sufficient. Ex post monotonicity is satisfied in all single crossing environments with strict ex post incentive constraints. We show by means of two classic examples that ex post monotonicity does not imply nor is it implied by Maskin monotonicity. The single unit auction with interdependent valuations is shown to satisfy ex post monotonicity but not Maskin monotonicity. We further describe a Pareto correspondence that fails ex post monotonicity but satisfies Maskin monotonicity.

Original languageEnglish (US)
Pages (from-to)527-566
Number of pages40
JournalGames and Economic Behavior
Issue number2
StatePublished - Jul 2008

All Science Journal Classification (ASJC) codes

  • Finance
  • Economics and Econometrics


  • Ex post equilibrium
  • Implementation
  • Interdependent values
  • Single crossing


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