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The impossibility of unbiased judgment aggregation (updated version)


  • Franz Dietrich

    (University of Maastricht, The Netherlands)

  • Christian List

    (London School of Economics, UK)


All existing impossibility theorems on judgment aggregation over logically connected propositions have one of two restrictions: they either use a controversial systematicity condition or apply only to special agendas of propositions with rich logical connections. An important open question is whether judgment aggregation faces any serious impossibilities without these restrictions. Here we prove the first impossibility theorem without systematicity that applies to all standard agendas: there exists no judgment aggregation rule satisfying universal domain, collective rationality, anonymity and a new condition called unbiasedness. For many agendas, anonymity can be weakened. Applied illustratively to (strict) preference aggregation represented in the judgment aggregation model, our result implies that every unbiased social welfare function with universal domain depends only on a single individual.

Suggested Citation

  • Franz Dietrich & Christian List, 2005. "The impossibility of unbiased judgment aggregation (updated version)," Public Economics 0510001, University Library of Munich, Germany, revised 31 Oct 2005.
  • Handle: RePEc:wpa:wuwppe:0510001
    Note: Type of Document - pdf; pages: 14

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    More about this item


    judgment aggregation; discursive dilemma; formal logics; impossibility theorem; unbiasedness; systematicity; agendas;

    JEL classification:

    • D70 - Microeconomics - - Analysis of Collective Decision-Making - - - General
    • D71 - Microeconomics - - Analysis of Collective Decision-Making - - - Social Choice; Clubs; Committees; Associations


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