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Party formation in single-issue politics


  • Martin J. Osborne
  • Rabee Tourky


We study party formation in a general model of collective decision-making, modelling parties as agglomerations of policy positions championed by decision-makers. We show that in the presence of economies of party size and a one-dimensional policy space, players agglomerate into exactly two parties. This result does not depend on the magnitude of the economies of party size or sensitively on the nature of the individuals' preferences. Our analysis encompasses several models, including decision-making in committees with costly participation and representative democracy in which the legislature is elected by citizens, for a wide range of electoral systems including plurality voting and proportional representation. The result implies that a multiplicity of parties hinges on the presence of more than one significant political issue or of diseconomies of party size.

Suggested Citation

  • Martin J. Osborne & Rabee Tourky, 2005. "Party formation in single-issue politics," Working Papers tecipa-174, University of Toronto, Department of Economics.
  • Handle: RePEc:tor:tecipa:tecipa-174

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    References listed on IDEAS

    1. Levy, Gilat, 2004. "A model of political parties," Journal of Economic Theory, Elsevier, vol. 115(2), pages 250-277, April.
    2. Ignacio Ortuno-Ortin & Anke Gerber, 1998. "Political compromise and endogenous formation of coalitions," Social Choice and Welfare, Springer;The Society for Social Choice and Welfare, vol. 15(3), pages 445-454.
    3. Martin J. Osborne & Al Slivinski, 1996. "A Model of Political Competition with Citizen-Candidates," The Quarterly Journal of Economics, Oxford University Press, vol. 111(1), pages 65-96.
    4. Jackson, Matthew O. & Moselle, Boaz, 2002. "Coalition and Party Formation in a Legislative Voting Game," Journal of Economic Theory, Elsevier, vol. 103(1), pages 49-87, March.
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    7. Jeffrey S. Rosenthal & Martin J. Osborne & Matthew A. Turner, 2000. "Meetings with Costly Participation," American Economic Review, American Economic Association, vol. 90(4), pages 927-943, September.
    8. Nicolaus Tideman, 1995. "The Single Transferable Vote," Journal of Economic Perspectives, American Economic Association, vol. 9(1), pages 27-38, Winter.
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    Cited by:

    1. Mattozzi, Andrea & Merlo, Antonio, 2015. "Mediocracy," Journal of Public Economics, Elsevier, vol. 130(C), pages 32-44.
    2. Mattozzi, Andrea & Merlo, Antonio, 2008. "Political careers or career politicians?," Journal of Public Economics, Elsevier, vol. 92(3-4), pages 597-608, April.
    3. Andrei Gomberg & Francisco Marhuenda & Ignacio Ortuño-Ortín, 2007. "Endogenous platforms: the case of many parties," International Journal of Game Theory, Springer;Game Theory Society, vol. 35(2), pages 223-249, January.
    4. Katsuya Kobayashi & Hideo Konishi, 2016. "Endogenous party structure," Economics of Governance, Springer, vol. 17(4), pages 317-351, November.
    5. Thomas Braendle, 2013. "Do Institutions Affect Citizens' Selection into Politics?," Working papers 2013/04, Faculty of Business and Economics - University of Basel.
    6. Ludovic Renou, 2011. "Group Formation and Governance," Journal of Public Economic Theory, Association for Public Economic Theory, vol. 13(4), pages 595-630, August.
    7. Eguia, Jon X., 2011. "Voting blocs, party discipline and party formation," Games and Economic Behavior, Elsevier, vol. 73(1), pages 111-135, September.
    8. Bandiera, Oriana & Levy, Gilat, 2010. "Diversity and the Power of the Elites in Democratic Societies: A model and a test," CEPR Discussion Papers 7985, C.E.P.R. Discussion Papers.
    9. Arnaud Dellis, 2013. "The two-party system under alternative voting procedures," Social Choice and Welfare, Springer;The Society for Social Choice and Welfare, vol. 40(1), pages 263-284, January.
    10. Arghya Ghosh & Kieron Meagher, 2014. "Voting on Infrastructure Investment: The Role of Product Market Competition," ANU Working Papers in Economics and Econometrics 2014-618, Australian National University, College of Business and Economics, School of Economics.
    11. Ghosh, Arghya & Meagher, Kieron, 2015. "The politics of infrastructure investment: The role of product market competition," Journal of Economic Behavior & Organization, Elsevier, vol. 119(C), pages 308-329.
    12. Jon X. Eguia, 2013. "The Origin of Parties: The United States Congress in 1789–1797 as a Test Case," Economics and Politics, Wiley Blackwell, vol. 25(3), pages 313-334, November.
    13. Ronald Peeters & Rene Saran & Ayşe Müge Yüksel, 2016. "Strategic party formation on a circle and Duverger’s Law," Social Choice and Welfare, Springer;The Society for Social Choice and Welfare, vol. 47(3), pages 729-759, October.
    14. Jon Eguia, 2012. "A spatial theory of party formation," Economic Theory, Springer;Society for the Advancement of Economic Theory (SAET), vol. 49(3), pages 549-570, April.
    15. Antonio Merlo, 2005. "Whither Political Economy? Theories, Facts and Issues," PIER Working Paper Archive 05-033, Penn Institute for Economic Research, Department of Economics, University of Pennsylvania, revised 01 Dec 2005.
    16. Peeters Ronald & Saran Rene & Yuksel Ayse Muge, 2010. "Strategic Party Formation on a Circle," Research Memorandum 045, Maastricht University, Maastricht Research School of Economics of Technology and Organization (METEOR).
    17. Pech, Gerald, 2012. "Intra-party decision making, party formation, and moderation in multiparty systems," Mathematical Social Sciences, Elsevier, vol. 63(1), pages 14-22.
    18. Motz, Nicolas, 2016. "How Political Parties Shape Electoral Competition," MPRA Paper 69351, University Library of Munich, Germany.

    More about this item

    JEL classification:

    • D70 - Microeconomics - - Analysis of Collective Decision-Making - - - General
    • D72 - Microeconomics - - Analysis of Collective Decision-Making - - - Political Processes: Rent-seeking, Lobbying, Elections, Legislatures, and Voting Behavior

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