Droop quota

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In the study of electoral systems, the Droop quota (sometimes called the Hagenbach-Bischoff, Britton, or Newland-Britton quota[1][a]) is the minimum number of supporters a party or candidate needs to receive in a district to guarantee they will win at least one seat in a legislature.[3][4]

The Droop quota is used to extend the concept of a majority to multiwinner elections, taking the place of the 50% bar in single-winner elections. Just as any candidate with more than half of all votes is guaranteed to be declared the winner in single-seat election, any candidate who holds more than a Droop quota's worth of votes is guaranteed to win a seat in a multiwinner election.[4]

Besides establishing winners, the Droop quota is used to define the number of excess votes, i.e. votes not needed by a candidate who has been declared elected. In proportional quota-based systems such as STV or expanding approvals, these excess votes can be transferred to other candidates, preventing them from being wasted.[4]

The Droop quota was first suggested by the English lawyer and mathematician Henry Richmond Droop (1831–1884) as an alternative to the Hare quota, which is a basic component of single transferable voting, a form of proportional representation.[4]

Today, the Droop quota is used in almost all STV elections, including those in Australia,[5] the Republic of Ireland, Northern Ireland, and Malta.[6] It is also used in South Africa to allocate seats by the largest remainder method.[7][8]

  1. ^ Lundell, Jonathan; Hill, ID (October 2007). "Notes on the Droop quota" (PDF). Voting Matters (24): 3–6.
  2. ^ Pukelsheim, Friedrich (2017). "Quota Methods of Apportionment: Divide and Rank". Proportional Representation. pp. 95–105. doi:10.1007/978-3-319-64707-4_5. ISBN 978-3-319-64706-7.
  3. ^ "Droop Quota", The Encyclopedia of Political Science, 2300 N Street, NW, Suite 800, Washington DC 20037 United States: CQ Press, 2011, doi:10.4135/9781608712434.n455, ISBN 978-1-933116-44-0, retrieved 2024-05-03{{citation}}: CS1 maint: location (link)
  4. ^ a b c d Droop, Henry Richmond (1881). "On methods of electing representatives" (PDF). Journal of the Statistical Society of London. 44 (2): 141–196 [Discussion, 197–202] [33 (176)]. doi:10.2307/2339223. JSTOR 2339223. Reprinted in Voting matters Issue 24 (October 2007) pp. 7–46.
  5. ^ "Proportional Representation Voting Systems of Australia's Parliaments". Electoral Council of Australia & New Zealand. Archived from the original on 6 July 2024.
  6. ^ https://electoral.gov.mt/ElectionResults/General
  7. ^ Pukelsheim, Friedrich (2014). Proportional representation : apportionment methods and their applications. Internet Archive. Cham ; New York : Springer. ISBN 978-3-319-03855-1.
  8. ^ "IFES Election Guide | Elections: South African National Assembly 2014 General". www.electionguide.org. Retrieved 2024-06-02.


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