The Disunity of Unanimity

16 Pages Posted: 28 Mar 2003

See all articles by Francesco Parisi

Francesco Parisi

University of Minnesota - Law School; University of Bologna

Jonathan Klick

University of Pennsylvania Carey Law School; Erasmus School of Law; PERC - Property and Environment Research Center


In the original position meta-bargain among political agents, each can achieve higher expected utility by binding himself to a unanimity rule, rather than risk the chance of being an excluded party in later period-by-period bargains. This argument is illustrated for a three-agent, constant-sum game where there are three reasonable voting rule options: 1) dictatorship rule; 2) majority rule; or 3) unanimity rule. Given concave utility functions, by Jensen's Inequality, each player would prefer the coalition inclusion guaranteed by the unanimity rule as opposed to the possible exclusion inherent in the other two options. However, once transactions costs are considered, a unanimity rule will create situations where all voters might agree in principle to a policy proposition, yet they will fail to reach a unanimous consensus.

Suggested Citation

Parisi, Francesco and Klick, Jonathan, The Disunity of Unanimity. Constitutional Political Economy, Vol. 14, No. 2, pp. 83-94, June 2003, George Mason Law & Economics Research Paper No. 01-28, Available at SSRN: or

Francesco Parisi (Contact Author)

University of Minnesota - Law School ( email )

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United States

University of Bologna ( email )

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Jonathan Klick

University of Pennsylvania Carey Law School ( email )

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Erasmus School of Law ( email )

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PERC - Property and Environment Research Center

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