Single-winner systems

Single-winner Voting Method Comparison Chart

There are many different ways to elect a single office, such as a president, governor or mayor. This chart compares the most widely discussed voting methods for electing a single winner (and thus does not deal with multi-seat or proportional representation methods). There are countless possible evaluation criteria. 

  Plurality Two-Round Runoff Ranked Choive Voting (RCV) Approval Range Condorcet methods Borda Count
Resistance to spoilers Low Medium High Medium Medium High Low
Later-no-harm criterion Yes Yes Yes No No No No
Resistance to strategic voting Low High High Low Low High Low
Majority-favorite criterion Yes Yes Yes No No Yes No
Mutual-majority criterion No No Yes No No Yes/No No
Prospects for U.S. adoption High High High Medium Low Low Low
Condorcet-loser criterion No Yes Yes No No Yes/No Yes
Condorcet-winner criterion No No No No No Yes No
Independence of clones criterion No No Yes Yes/No Yes/No Yes/No No
Monotonicity criterion Yes No No Yes Yes Yes/No

Yes

References

Austen-Smith, David, and Jeffrey Banks (1991). “Monotonicity in Electoral Systems”. American Political Science Review, Vol. 85, No. 2 (June): 531-537.

Brewer, Albert P. (1993). “First- and Second-Choice Votes in Alabama”. The Alabama Review, A Quarterly Review of Alabama History, Vol. 46 (April 1993): 83 - 94

Burgin, Maggie (1931). The Direct Primary System in Alabama. Masters thesis, University of Alabama.

Green-Armytage, James (n.d.). “A Survey of Basic Voting Methods”. Web page at http://fc.antioch.edu/~james_green-armytage/vm/survey.htm (last visited November 20, 2008).

Green-Armytage, James (2008). “Strategic Voting and Strategic Nomination: Comparing seven election methods”. Unpublished manuscript, University of California at Santa Barbara. http://fc.antioch.edu/~james_green-armytage/vm/svn.pdf (last visited November 20, 2008).

Nagel, Jack (2007). “The Burr Dilemma in Approval Voting”. Journal of Politics, Vol. 69, No. 1 (February): 43-58.

Robert, Henry M., William J. Evans, Daniel H. Honemann, Thomas J. Balch (2000). Robert's Rules of Order Newly Revised, 10th Edition. Cambridge, MA, Da Capo Press.

Tideman, Nicolaus (2006). Collective Decisions and Voting: The Potential for Public Choice

 

For a full explanation, refer to our archived site.

Notes:

Plurality Voting is the most prevalent method of voting in the U.S. In a single seat election, the voter picks one candidate, and the candidate selected by the largest number of voters is elected, regardless of whether that candidate is favored by a majority or not. Because of its supposed similarity to a horse race this method is sometimes referred to as "First Past the Post" or FPTP.

Two-Round Runoff: Two-round Runoffs are intended to prevent split majorities resulting in the election of a candidate that the majority opposes. The winner of the second round is considered a majority winner, although, due to drop-off in turnout, this "winner" could receive fewer votes in the runoff than the loser received in the first round. Thus the "majority" is manufactured by preventing voters from voting for eliminating candidates and discounting all voters who do not turn out for the second round.

Ranked Choice Voting (RCV): Ranked choice voting has several variants and other names, including Instant Runoff Voting (IRV), Preferential Voting, and the "Alternative Vote." Voters are allowed to rank candidates in order of choice using a single transferable vote. If no candidate is the first choice of a majority of voters, candidates are sequentially dropped from the bottom, with ballots that were credited towards these candidates then being credited to those voters' next choice who has not been eliminated. This simulation of a series of runoffs ends when one candidate receives a majority or only one candidate remains. This method of voting was invented in Massachusetts around 1870, based on the "single transferable vote" innovation developed some decades previously. It is described in Robert's Rules of Order (Robert, et al., 2000: 411-414), and is used for government elections in places such as the U.S., Ireland and Australia.

Approval: Approval Voting allows voters to vote for as many candidates as they wish in a single-seat election, with the candidate receiving the most votes being elected. Thus some voters may cast one vote, while others effectively may cast several. Since this method is not used in government elections it has not been constitutionally tested as to whether it complies with the one-person, one-vote mandate.

Range: Range Voting asks each voter to assign a score (such a 0 - 10) to each candidate, with the candidate with the highest average score being elected. It is used in sporting events with impartial judges and Internet scoring of various products or services. Because this method is highly susceptible to strategy, it is most appropriate when voting is conducted by disinterested judges, rather than voters with a stake in the outcome.

Condorcet methods: Named after the Marquis de Condorcet who invented it around the time of the French Revolution. Voters are asked to rank all candidates. There rankings can be used to do a pair-wise comparison of how each candidate would theoretically do in a head-to-head match up with each other candidate one at a time. If there is one candidate who would defeat each of the others in a one-on-one contest, this candidate is termed the "Condorcet winner." In some scenarios there is no such winner, as a cycle where A would beat B, B would beat C and C would beat A exists (think of rock, paper, scissors). In this case a variety of different procedures (often named for the inventor) have been proposed for settling which candidate should win.

Borda Count: Borda Count, named after its inventor Jean-Charles de Borda around the time of the French revolution, asks voters to rank all candidates in order of preference. Based on this order, the candidates are assigned a score, with the first choice receiving the most points, the second choice receiving a smaller, number, etc. with the last candidate receiving no points. In one sense, it is like Range voting, except that the points are inflexibly tied to the ranking order, rather than set by the voters individually. Because it is highly susceptible to strategy, like Range Voting, it is most suitable for elections by impartial judges, rather than voters with a stake in the outcome.

 

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