Duverger's law

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Duverger's law holds that plurality-rule elections (such as first past the post) structured within single-member districts tend to favor a two-party system, whereas "the double ballot majority system and proportional representation tend to favor multipartism".[1][2] The discovery of this tendency is attributed to Maurice Duverger, a French sociologist who observed the effect and recorded it in several papers published in the 1950s and 1960s.

Duverger's law draws from a model of causality from the electoral system to a party system. A proportional representation (PR) system creates electoral conditions that foster the development of many parties, whereas a plurality system marginalizes smaller political parties, generally resulting in a two-party system.

Most countries with plurality voting have representation in their legislatures by more than two parties. While the United States is very much a two-party system, the United Kingdom, Canada and India have consistently had multiparty parliaments.[3][4]. However, only the two dominant parties of their times have formed governments in the United Kingdom and Canada. Eric Dickson and Ken Scheve argue that there is a counter force to Duverger's law, that on the national level a plurality system encourages two parties, but in the individual constituencies supermajorities will lead to the vote fracturing.[5] Steven R. Reed has shown Duverger's law to work in Japan[6] and Italy.[7]

See also

Wikipedia: two-party system, multi-party system, party system


  1. Grzymala-Busse, Anna (31 December 2014). "Remembering Duverger". Mischiefs of Faction. Archived from the original on 4 May 2016. Retrieved 28 April 2016.
  2. Sartori, Giovanni (1994). Comparative Constitutional Engineering: An Inquiry into Structures, Incentives and Outcomes. Macmillan.
  3. Dunleavy, Patrick (18 June 2012). "Duverger's Law is a dead parrot. Outside the USA, first-past-the-post voting has no tendency at all to produce two party politics". blogs.lse.ac.uk.
  4. Dunleavy, Patrick; Diwakar, Rekha (2013). "Analysing multiparty competition in plurality rule elections" (PDF). Party Politics. 19 (6): 855–886. doi:10.1177/1354068811411026.
  5. Dickson, Eric S.; Scheve, Kenneth (2010). "Social Identity, Electoral Institutions and the Number of Candidates" (PDF). British Journal of Political Science. 40 (2): 349–375. CiteSeerX doi:10.1017/s0007123409990354. JSTOR 40649446. Archived from the original (PDF) on 2018-07-21. Retrieved 2017-10-26.
  6. Reed, Steven R. (1990). "Structure and Behaviour: Extending Duverger's Law to the Japanese Case". British Journal of Political Science. 20 (3): 335–356. doi:10.1017/S0007123400005871. JSTOR 193914.
  7. Reed, Steven R. (2010). "Duverger's Law is Working in Italy". Comparative Political Studies. 34 (3): 312–327. doi:10.1177/0010414001034003004.
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