Ranked voting system

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Preferential voting or rank voting describes certain voting systems in which voters rank outcomes in a hierarchy on the ordinal scale. When choosing between more than two options, preferential voting systems provide a number of advantages over first-past-the-post voting (also called plurality voting). This does not mean that preferential voting is always the best system; Arrow's impossibility theorem proves that no method can simultaneously obtain all properties desirable in a voting system.[Mankiw 1] There is likewise no consensus among academics or public servants as to the best electoral system.[1]

There are many types of preferential voting, but currently only instant-runoff voting (alternative vote) and single transferable vote are used in governmental elections. Instant runoff voting is employed in Australia at the state and federal levels, in Ireland for its presidential elections, and by some cities in the United States, United Kingdom, and New Zealand. The single transferable vote is used for national elections in the Republic of Ireland and Malta, for regional and local elections in Northern Ireland, for all local elections in Scotland, and for some local elections in New Zealand and the United States.

Variety of systems[edit]

There are many preferential voting systems, so it is sometimes difficult to distinguish between them.

Selection of the Condorcet winner is generally considered by psephologists as the ideal election outcome,[2] so "Condorcet efficiency" is important when evaluating different methods of preferential voting.[3] This choice is also the one that would win every two-way contest against every other alternative.[Mankiw 2]

Another criterion used to gauge the effectiveness of a preferential voting system is its ability to withstand manipulative voting strategies,[4] when voters cast ballots that do not reflect their preferences in the hope of electing their first choice. This can be rated on at least two dimensions—the number of voters needed to game the system[5] and the complexity of the mechanism necessary.[citation needed]

Instant-runoff or preferential voting[edit]

Used in national elections in Australia, this system simulates a series of runoff elections. If no candidate is the first choice of more than half of the voters, then all votes cast for the candidate with the fewest number of first choices are added to the totals of the top-ranked candidate still in the race.[6] If this does not result in any candidate receiving a majority, further rounds of redistribution occur.[6]

This method is thought to be resistant to manipulative voting as the only strategies that work against it require voters to highly rank choices they actually want to see lose.[G&F 1] At the same time, this system fails the monotonicity criterion, where ranking a candidate higher can lessen the chances he or she will be elected. Additionally, alternative voting has a lower Condorcet efficiency than similar systems when there are more than four choices.[G&F 2]

Borda count[edit]

In the Borda count, ballots are counted by assigning a point value to each place in each voter's ranking of the candidates, and the choice with the largest number of points overall is elected.[Mankiw 1] This method is named after its inventor, French mathematician Jean-Charles de Borda.[Mankiw 1] Instead of selecting a Condorcet winner, this system may select a choice that reflects an average of the preferences of the constituency.[citation needed]

This system suffers from the fact that the outcome it selects is dependent on the other choices present[clarification needed]. That is, the Borda count does not exhibit independence of irrelevant alternatives[Mankiw 1] or independence of clones. The Borda count can be easily manipulated by adding candidates, called clones, whose views are identical to the preferred candidate's. An example of this strategy can be seen in Kiribati's 1991 Presidential nomination contest.[7]

Single transferable vote[edit]

This is currently one of the preferential voting systems most used by countries and states.[notes 1] It uses multi-member constituencies. Any candidates that achieve the number of votes required for election (the "quota") are elected and their surplus votes are redistributed to the voter's next choice candidate.[CEPPS 1] Once this is done, if not all places have been filled then the candidate with the smallest amount of votes is eliminated, and their votes are also redistributed to the voter's next choice. This whole process is repeated until all seats are filled. This method is also called the Hare-Clark system.[CEPPS 1]

  1. ^ See table in use by polities below

Superiority v. FPTP[edit]

When choosing between more than two options, preferential voting achieves outcomes better than those produced by a first-past-the-post system. When endorsing a switch to a preferential voting system in 2011, British politician Nick Clegg stated, "first-past-the-post leads to a whole host of problems... it means MPs can go about their business without ever having to appeal to a majority of their own constituents...".[9] He also stated that a preferential voting method like instant runoff voting would result in politicians "work[ing] harder to appeal to more people than before".[9] Academic experts have also rejected first-past-the-post; at a 2011 LSE workshop attended by 22 voting theory specialists, none endorsed first-past-the-post as the "best voting procedure".[10]

The first-past-the-post system will indeed occasionally elect a candidate who would have lost out to every other option in a two-way contest (the so-called Condorcet loser) by splitting the opposition vote. It happens even more frequently (for a similar reason) that the winner is not the Condorcet winner.[Mankiw 2]

Many countries use a two-round system (a runoff election) to improve the fairness of the election.

Many arguments for preferential voting being superior to first-past-the-post rely to some extent on several assumptions: that voters have single peaked preferences over a single dimension (e.g. liberal v. conservative), that choices can be placed on a continuum, and that voters know accurately where each candidate lies on that continuum. However even if these assumptions are only partially true, the first-past-the-post system is still likely to be less fair.

Uniqueness of votes[edit]

If there are a large number of candidates, which is quite common in Single transferable vote elections, then it is likely that many preference voting patterns will be unique to individual voters.[11][12] For example, in the Irish general election, 2002, the electronic votes were published for the Dublin North constituency.[13] There were 12 candidates and almost 44,000 votes cast. The most common pattern (for the three candidates from one party in a particular order) was chosen by only 800 voters, and more than 16,000 patterns were chosen by just one voter each.

The number of possible complete rankings with no ties is the factorial of the number of candidates, N, but with ties it is equal to the corresponding ordered Bell number and is asymptotic to

\frac{N!}{2(\ln 2)^{N+1}}.[14]

In the case common to IRV in which no ties are allowed, except for unranked candidates who are tied for last place, the number of possible rankings for N candidates is precisely

 \sum_{n=1}^{N-1} \frac{N!}{n!} = \lfloor (e-1)N! - 1 \rfloor = \mathrm{floor}\left( (e-1)N! - 1 \right).[15]

Use by polities[edit]

Countries
Nation Year of first use Type Notes
Australia 1918[16] single transferable vote, alternative vote From 1949, the single transferable vote method has been used for upper house legislative elections.[Sawer 1] Alternative vote is used for lower house elections.[CEPPS 2]
Austria 1949[17] open list[1]
Belgium 1945[17] open list[1]
Brazil x open list[18]
Chile[18] 1958-1973 open list
Colombia[CEPPS 3] x open list Political parties choose between open list and closed list
Cyprus x open list[1]
Czech Republic[CEPPS 4] x contingent vote only used to decide lower house legislative elections
Denmark 1945[17] open list[1]
Estonia x open list[CEPPS 5] As of 2001 single transferable vote had been in use since 1990 to decide legislative elections.[Sawer 1] This is no longer the case.[CEPPS 5] Estonia's current open list system may not actually be a preferential voting system as it may be that voters cast only one preference vote.
Fiji[19] 1998 alternative vote
Finland 1945[17] open list[1]
Greece 1975-1984, 1996[17] open list[1]
Hong Kong 1998[20] alternative vote[21] alternative vote is only used in the 4 smallest of Hong Kong's 29 functional constituencies.[22] Officially called preferential elimination voting, the system is identical to the alternative vote.[21]
Indonesia 2004[23] open list only used to decided the elections of one legislative chamber[CEPPS 6]
Iraq[24] 2009 open list
Ireland[Sawer 1] 1922 alternative vote, single transferable vote Single transferable vote is used to decide legislative elections only.[Sawer 1] Since 1937 Ireland has used the alternative vote to decide presidential elections.[Sawer 1]
Italy 1946-1994[17] open list[25]
Latvia[CEPPS 7] x open list only used to decide legislative elections
Liechtenstein x open list[1]
Luxembourg 1945[17] open list[CEPPS 8]
Malta[Sawer 1] 1921 single transferable vote
Nauru 1968[Sawer 1] Borda count[CEPPS 9] Nauru uses the Dowdall system, which is an improved version of the Borda count.[CEPPS 9]
Netherlands 1945[17] open list[CEPPS 10] only used to decide lower house legislative elections[CEPPS 10]
New Zealand x single transferable vote[26] alternative vote is used in only some elections, such as district health boards as well as some city and district councils.[26]
Northern Ireland 1973[Sawer 1] single transferable vote[27]
Norway 1945[17] open list[CEPPS 11]
Papua New Guinea 2007[28] alternative vote[G&F 3] Between 1964 and 1975 PNG used a system that allowed voters the option of ranking candidates.[Sawer 1] Currently, voters must rank only their top three choices.[29]
San Marino x open list[1]
Slovakia[CEPPS 12] x open list only used to decide legislative elections
Slovenia 2000[30] open list[CEPPS 13] Open list is only used to decide lower house legislative elections, and two seats, which are reserved for Hungarian and Italian minorities, are decided using a Borda count.[CEPPS 13]
Sri Lanka[Sawer 2] 1978 contingent vote and open list[CEPPS 14] In Sri Lanka contingent vote is used to decide presidential elections[Sawer 1] and legislative elections, open list.[CEPPS 14]
Switzerland x open list[18]
Zimbabwe[31] 1979-1985 alternative vote only used for white candidates
Federated states
Province/state Country Years in use Type Notes
Alberta[Sawer 1] Canada 1952-1954 open list
Australian Capital Territory[Sawer 1] Australia 1993–present single transferable vote
British Columbia[Sawer 1] Canada 1926-1955 open list
Manitoba[Sawer 1] Canada 1927-1936 open list
New South Wales[Sawer 1] Australia 1918–present single transferable vote (1918-1926), contingent vote (1926-1928), alternative vote (1929-1980), open list (1981–present) Since 1978, NSW has used the single transferable vote method to decide upper house legislative elections only.
Northern Territory[Sawer 1] Australia 1980 only[citation needed] x
Queensland[Sawer 1] Australia 1892-1942, 1962–present contingent vote (1892-1942), alternative vote (1962-1992), open list (1992–present)
South Australia[Sawer 1] Australia 1929-1935, 1982–present Alternative vote in multi-member districts (1929-1935), single transferable vote (1982–present) used to decide upper house legislative elections only
Tasmania[Sawer 1] Australia 1907–present single transferable vote Since 1909, alternative vote voting has been used in Tasmania to decide upper house legislative elections.
Victoria[Sawer 1] Australia 1911–present open list (1911-1915), alternative vote (1916–present) Prior to 1916, Victoria did not use any preferential voting method to decide upper house legislative elections.
Western Australia[Sawer 1] Australia 1907–present open list (1907-1911), alternative vote (1912–present) Since 1989, Western Australia has used the single transferable vote method to decide upper house legislative elections
International organizations
Organization Year of first use Type Notes
European Union[CEPPS 15] x option to use single transferable vote Member countries can use either proportional representation (not a type of preferential voting)[citation needed] or single transferable vote to elect MEPs
Municipalities
City/town Years in use Type Notes
Ann Arbor, MI[32] 1975 only alternative vote
Aspen, CO[33] 2009 only alternative vote
Berkeley, CA[34] 2010–present alternative vote
Burlington, VT[35] 2005-2010 alternative vote
Hendersonville, NC[36] 2007–present alternative vote part of a statewide pilot program[37]
London 2000[38]-present supplementary vote[39]
Memphis, TN[6] 2011–present alternative vote
Minneapolis, MN[40] 2009–present alternative vote
Oakland, CA[34] 2010–present alternative vote
Portland, ME[6] 2011–present alternative vote
San Francisco 2004[41]-present alternative vote[6]
San Leandro, CA[34] 2010–present alternative vote
St. Paul, MN 2011[42]-present alternative vote[43]
Takoma Park, MD[44] 2006–present alternative vote
Telluride, CO[45] 2011–present alternative vote

See also[edit]

External links[edit]

References[edit]

  1. ^ a b c d e f g h i "Electoral Systems in Europe: An Overview". European Parliament in Brussels: European Centre for Parliamentary Research and Documentation. October 2000. Retrieved July 6, 2012. 
  2. ^ Saari, Donald (1995). Basic Geometry of Voting. Springer. p. 46. ISBN 9783540600640. 
  3. ^ Gofman and Feld, 2004, pp. 649
  4. ^ Gofman and Feld, 2004, pp. 647
  5. ^ Gofman and Feld, 2004, pp. 652
  6. ^ a b c d e Bialik, Carl (May 14, 2011). "Latest Issue on the Ballot: How to Hold a Vote". Wall Street Journal. Retrieved June 29, 2012. 
  7. ^ Reilley, Benjamin. "Social Choice in the South Seas: Electoral Innovation and the Borda Count in the Pacific Island Countries". International Political Science Review (2002), Vol 23, No. 4, 355–372
  8. ^ a b Nick Clegg (18 February 2011). Votes referendum: Deputy PM Nick Clegg's speech in full. BBC. 
  9. ^ "Voting experts unanimously reject First Past the Post". London School of Economics and Political Science. 21 April 2011. Retrieved June 29, 2012. 
  10. ^ Election database 1st February 2004
  11. ^ Irish Commission on Electronic Voting 2004
  12. ^ Dublin County Returning Officer complete table of votes cast Dublin North (zip file)
  13. ^ Wilf, Herbert S. (January 1994) [1990]. "Chapter 5: Analytic and asymptotic methods". generatingfunctionology (Second Edition ed.). Academic Press. pp. 175–176. ISBN 0-12-751956-4. Retrieved 2006-08-06. 
  14. ^ OEIS A007526
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  18. ^ "Section 54: Voting and other matters". Constitution of Fiji. International Constitutional Law Project. Retrieved June 29, 2012. 
  19. ^ The fact that Hong Kong began using preferential voting in 1998 can be seen from two sources:
    • Minutes from a 1997 LegCo meeting include a proposal to use "preferential elimination voting" for the three smallest functional constituencies. See, "Legislative Council Bill (Minutes) 11 Sept 97". The Legislative Council Commission. Retrieved July 2, 2012. 
    • 1998 is the first year "preferential elimination voting" can be found in the Hong Kong yearbook. See, "The Electoral System: b. Functional Constituency". Hong Kong Yearbook 1998. Government Information Centre of Hong Kong. Retrieved July 2, 2012. 
  20. ^ a b "Ch. 3, FUNCTIONAL CONSTITUENCIES: The Preferential Elimination System of the 4 SFCs". Guidelines on Election-related Activities in respect of the Legislative Council Election. Hong Kong Electoral Affairs Comisson. Retrieved June 29, 2012. 
  21. ^ "Functional Constituency Elections". 2000 Legislative Council Elections. Hong Kong Electoral Affairs Commission. 2000. Retrieved June 29, 2012. 
  22. ^ "Indonesia: Continuity, Deals and Consensus". Electoral Systems. ACE Electoral Knowledge Network. Retrieved July 6, 2012. 
  23. ^ Bruno, Greg (February 5, 2009). "Reshuffling the Political Deck". Backgrounder: Iraq's Political Landscape. Council on Foreign Relations. Retrieved July 8, 2012. 
  24. ^ Miriam A. Golden, Lucio Picci (April 2008). "Pork-Barrel Politics in Postwar Italy, 1953-94". American Journal of Political Science 52 (2). 
  25. ^ a b "STV - It's Simple To Vote". New Zealand Department of Internal Affairs. 2010. Retrieved June 29, 2012. 
  26. ^ "Frequently Asked Questions - PR/STV Voting System". Electoral Office for Northern Ireland. 2006. Retrieved June 29, 2012. 
  27. ^ Blackwell, Eoin (June 20, 2012). "Observers urge peaceful PNG election". The Sydney Morning Herald. Retrieved June 29, 2012. 
  28. ^ "Voting". Electoral Commission of Papua New Guinea. 2011. Retrieved June 30, 2012. 
  29. ^ "Article 80: The National Assembly; Composition and Election". Constitution of the Republic of Slovenia. United Nations Public Administration Network. pp. 47–48. Retrieved July 3, 2012. 
  30. ^ "Negotiations". Administration and Cost of Elections Project. ACE Electoral Knowledge Network. Retrieved July 6, 2012. 
  31. ^ "Instant Runoff Voting (IRV): History of Use in Ann Arbor". Green Party of Michigan. 1998. Retrieved June 29, 2012. 
  32. ^ Urquhart, Janet (June 28, 2012). "Marks prevails in lawsuit over Aspen election ballots". The Aspen Times. Retrieved June 29, 2012. 
  33. ^ a b c "Ranked-Choice Voting". Alameda County Registrar of Voters. Retrieved June 29, 2012. 
  34. ^ McCrea, Lynne (03/03/10). vote-voting/ "Burlington Voters Repeal Instant Runoff Voting". Vermont Public Radio. Retrieved June 29, 2012. 
  35. ^ "New Voting Method for November 6, 2007: Hendersonville Pilots Instant Runoff Voting". Henderson County Board of Elections. 2007. Retrieved June 29, 2012. 
  36. ^ Harbin, John (April 8, 2011). "Hendersonville votes to keep instant runoff ballots". BlueRidgeNow.com. Times-News. Retrieved June 29, 2012. 
  37. ^ "London's elections: How the voting works". BBC. 3 May 2000. Retrieved June 29, 2012. 
  38. ^ "Voting systems in the UK". Parliament of the United Kingdom. Retrieved June 29, 2012. 
  39. ^ Gilbert, Curtis (November 2, 2009). "Instant runoff voting FAQ". Minnesota Public Radio. Retrieved June 29, 2012. 
  40. ^ Poundstone, William (2009). Gaming the Vote: Why Elections Aren't Fair (And What We Can Do About It). Macmillan. p. 170. ISBN 9780809048922. 
  41. ^ Baran, Madeleine (November 7, 2011). "Election Day in St. Paul Tuesday". Minnesota Public Radio. Retrieved June 29, 2012. 
  42. ^ "Ranked Voting Information". Ramsey County. Retrieved June 29, 2012. 
  43. ^ "CITY OF TAKOMA PARK ELECTION 2011". City Of Takoma Park. 2011. Retrieved June 29, 2012. 
  44. ^ "Instant Runoff Voting Brochure". Town of Telluride. 2011. Retrieved June 29, 2012. 
  1. ^ a b c d Principles of Microeconomics. p. 475. 
  2. ^ a b Gregory Mankiw (2012). Principles of Microeconomics (6 ed.). South-Western Cengage Learning. pp. 478–479. ISBN 978-0-538-45304-2. 
  1. ^ a b c d e f g h i j k l m n o p q r s t u Sawer, Marian (2001). Elections: Full, Free & Fair. Federation Press. p. 93. ISBN 9781862873957. 
  2. ^ Elections: Full, Free & Fair. p. 95. 
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  1. ^ Gofman and Feld, 2004, pp. 652
  2. ^ Gofman and Feld, 2004, pp. 647
  3. ^ Bernard Grofman, Scott L. Feld (2004). "If you like the alternative vote (a.k.a. the instant runoff), then you ought to know about the Coombs rule". Electoral Studies 23: 653.