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A Spatial Voting Model Where Proportional Rule Leads to Two-Party Equilibria


  • Francesco De Sinopoli

    () (Universidad Carlos III de Madrid - Department of Economics)

  • Giovanna Iannantuoni

    () (Universidad Carlos III de Madrid - Department of Economics)


n this paper we show that in a simple spatial model where the government is chosen under strict proportional rule, if the outcome function is a linear combination of parties' positions, with coefficient equal to their share of votes, essentially only a two-party equilibrium exists. The two parties taking a positive number of votes are the two extremist ones. Applications of this result include an extension of the well-known Alesina and Rosenthal model of divided government as well as a modified version of Besley and Coate's model of representative democracy. Different outcome functions are then analyzed.

Suggested Citation

  • Francesco De Sinopoli & Giovanna Iannantuoni, 2003. "A Spatial Voting Model Where Proportional Rule Leads to Two-Party Equilibria," CEIS Research Paper 31, Tor Vergata University, CEIS.
  • Handle: RePEc:rtv:ceisrp:31

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    References listed on IDEAS

    1. Ignacio OrtuÓo-OrtÎn, 1997. "A spatial model of political competition and proportional representation," Social Choice and Welfare, Springer;The Society for Social Choice and Welfare, vol. 14(3), pages 427-438.
    2. repec:cup:apsrev:v:89:y:1995:i:02:p:327-343_09 is not listed on IDEAS
    3. Francesco De Sinopoli, 2000. "Sophisticated voting and equilibrium refinements under plurality rule," Social Choice and Welfare, Springer;The Society for Social Choice and Welfare, vol. 17(4), pages 655-672.
    4. Roger B. Myerson & Robert J. Weber, 1988. "A Theory of Voting Equilibria," Discussion Papers 782, Northwestern University, Center for Mathematical Studies in Economics and Management Science.
    5. Elhanan Helpman & Gene M. Grossman, 1999. "Competing for Endorsements," American Economic Review, American Economic Association, vol. 89(3), pages 501-524, June.
    6. Timothy Besley & Stephen Coate, 1997. "An Economic Model of Representative Democracy," The Quarterly Journal of Economics, Oxford University Press, vol. 112(1), pages 85-114.
    7. Alesina, Alberto & Rosenthal, Howard, 1996. "A Theory of Divided Government," Econometrica, Econometric Society, vol. 64(6), pages 1311-1341, November.
    8. repec:cup:apsrev:v:87:y:1993:i:01:p:102-114_09 is not listed on IDEAS
    9. Alesina, Alberto & Rosenthal, Howard, 2000. "Polarized platforms and moderate policies with checks and balances," Journal of Public Economics, Elsevier, vol. 75(1), pages 1-20, January.
    10. repec:hrv:faseco:34222831 is not listed on IDEAS
    11. repec:cup:apsrev:v:82:y:1988:i:02:p:405-422_08 is not listed on IDEAS
    12. repec:cup:apsrev:v:76:y:1982:i:04:p:753-766_18 is not listed on IDEAS
    13. Austen-Smith, David & Banks, Jeffrey, 1988. "Elections, Coalitions, and Legislative Outcomes," American Political Science Review, Cambridge University Press, vol. 82(02), pages 405-422, June.
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    More about this item


    Voting; Proportional Rule; Nash Equilibria;

    JEL classification:

    • C72 - Mathematical and Quantitative Methods - - Game Theory and Bargaining Theory - - - Noncooperative Games
    • D72 - Microeconomics - - Analysis of Collective Decision-Making - - - Political Processes: Rent-seeking, Lobbying, Elections, Legislatures, and Voting Behavior


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