Working Paper No. 01-28:
The Disunity of Unanimity


Francesco Parisi, Jonathan Klick

Date Posted: 2001

Abstract (below)
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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.