Trading Votes for Votes. A Decentralized Matching Algorithm

58 Pages Posted: 28 Oct 2015

See all articles by Alessandra Casella

Alessandra Casella

Columbia University - Graduate School of Arts and Sciences, Department of Economics; Centre for Economic Policy Research (CEPR); National Bureau of Economic Research (NBER)

Thomas R. Palfrey

California Institute of Technology - Division of the Humanities and Social Sciences

Multiple version iconThere are 2 versions of this paper

Date Written: October 2015

Abstract

Vote-trading is common practice in committees and group decision-making. Yet we know very little about its properties. Inspired by the similarity between the logic of sequential rounds of pairwise vote-trading and matching algorithms, we explore three central questions that have parallels in the matching literature: (1) Does a stable allocation of votes always exists? (2) Is it reachable through a decentralized algorithm? (3) What welfare properties does it possess? We prove that a stable allocation exists and is always reached in a finite number of trades, for any number of voters and issues, for any separable preferences, and for any rule on how trades are prioritized. Its welfare properties however are guaranteed to be desirable only under specific conditions. A laboratory experiment confirms that stability has predictive power on the vote allocation achieved via sequential pairwise trades, but lends only weak support to the dynamic algorithm itself.

Keywords: algorithms, matching, vote trading, voting

JEL Classification: C92, D7, D72, P16

Suggested Citation

Casella, Alessandra and Palfrey, Thomas R., Trading Votes for Votes. A Decentralized Matching Algorithm (October 2015). CEPR Discussion Paper No. DP10908, Available at SSRN: https://ssrn.com/abstract=2682595

Alessandra Casella (Contact Author)

Columbia University - Graduate School of Arts and Sciences, Department of Economics ( email )

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Thomas R. Palfrey

California Institute of Technology - Division of the Humanities and Social Sciences ( email )

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