Strategy-proof judgement aggregation

F.K. Dietrich, C. List

Research output: Contribution to journalArticleAcademicpeer-review

Abstract

Which rules for aggregating judgments on logically connected propositions are manipulable and which not? In this paper, we introduce a preference-free concept of non-manipulability and contrast it with a preference-theoretic concept of strategy-proofness. We characterize all non-manipulable and all strategy-proof judgment aggregation rules and prove an impossibility theorem similar to the Gibbard-Satterthwaite theorem. We also discuss weaker forms of non-manipulability and strategy-proofness. Comparing two frequently discussed aggregation rules, we show that "conclusion-based voting" is less vulnerable to manipulation than "premise-based voting", which is strategy-proof only for "reason-oriented" individuals. Surprisingly, for "outcome-oriented" individuals, the two rules are strategically equivalent, generating identical judgments in equilibrium. Our results introduce game-theoretic considerations into judgment aggregation and have implications for debates on deliberative democracy.
Original languageEnglish
Pages (from-to)269-300
Number of pages31
JournalEconomics and Philosophy
Volume23
DOIs
Publication statusPublished - 1 Jan 2007

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