Difference between revisions of "Borda count"
(→Variants: caps) 
(→Variants: caps) 

Line 67:  Line 67:  
*Ballots that do not rank all the candidates can be allowed in three ways.  *Ballots that do not rank all the candidates can be allowed in three ways.  
**One way to allow leaving candidates unranked is to leave the scores of each ranking unchanged and give unranked candidates 0 points. For example, if there are 10 candidates, and a voter votes for candidate A first and candidate B second, leaving everyone else unranked, candidate A receives 9 points, candidate B receives 8 points, and all other candidates receive 0. This, however, facilitates strategic voting in the form of [[bullet voting]]: voting only for one candidate and leaving every other candidate unranked. This variant makes a bullet vote more effective than a fullyranked vote. This variant would satisfy the [[Plurality criterion]], the [[Favorite Betrayal criterion]] and the [[Noncompulsory support criterion]].  **One way to allow leaving candidates unranked is to leave the scores of each ranking unchanged and give unranked candidates 0 points. For example, if there are 10 candidates, and a voter votes for candidate A first and candidate B second, leaving everyone else unranked, candidate A receives 9 points, candidate B receives 8 points, and all other candidates receive 0. This, however, facilitates strategic voting in the form of [[bullet voting]]: voting only for one candidate and leaving every other candidate unranked. This variant makes a bullet vote more effective than a fullyranked vote. This variant would satisfy the [[Plurality criterion]], the [[Favorite Betrayal criterion]] and the [[Noncompulsory support criterion]].  
−  **Another way, called the ''modified Borda count'', is to assign the points up to ''k'', where k is the number of candidates ranked on a ballot. For example, in the modified Borda count, a ballot that ranks candidate A first and candidate B second, leaving everyone else unranked, would give 2 points to A and 1 point to B. This variant would not satisfy the [[Plurality criterion]], the [[Favorite Betrayal criterion]], or the [[Noncompulsory support criterion]].  +  **Another way, called the ''modified Borda count'', is to assign the points up to ''k'', where k is the number of candidates ranked on a ballot. For example, in the modified Borda count, a ballot that ranks candidate A first and candidate B second, leaving everyone else unranked, would give 2 points to A and 1 point to B. This variant would ''not'' satisfy the [[Plurality criterion]], the [[Favorite Betrayal criterion]], or the [[Noncompulsory support criterion]]. 
**The third way is to employ a uniformly truncated ballot obliging the voter to rank a certain number of candidates, while not ranking the remainder, who all receive 0 points. This variant would satisfy the same criteria as the Borda count.  **The third way is to employ a uniformly truncated ballot obliging the voter to rank a certain number of candidates, while not ranking the remainder, who all receive 0 points. This variant would satisfy the same criteria as the Borda count.  
Revision as of 16:35, 10 September 2005
The Borda count is a voting system used for singlewinner elections in which each voter rankorders the candidates.
The Borda count was devised by JeanCharles de Borda in June of 1770. It was first published in 1781 as MÃƒÂ©moire sur les ÃƒÂ©lections au scrutin in the Histoire de l'AcadÃƒÂ©mie Royale des Sciences, Paris. This method was devised by Borda to fairly elect members to the French Academy of Sciences and was used by the Academy beginning in 1784 until quashed by Napoleon in 1800.
The Borda count is classified as a positional voting system because each rank on the ballot is worth a certain number of points. Other positional methods include firstpastthepost (plurality) voting, and minor methods such as "vote for any two" or "vote for any three".
Contents
Procedures
Each voter rankorders all the candidates on their ballot. If there are n candidates in the election, then the firstplace candidate on a ballot receives n1 points, the secondplace candidate receives n2, and in general the candidate in ith place receives ni points. The candidate ranked last on the ballot therefore receives zero points.
The points are added up across all the ballots, and the candidate with the most points is the winner.
An example of an election
Imagine that Tennessee is having an election on the location of its capital. The population of Tennessee is concentrated around its four major cities, which are spread throughout the state. For this example, suppose that the entire electorate lives in these four cities, and that everyone wants to live as near the capital as possible.
The candidates for the capital are:
 Memphis on Wikipedia, the state's largest city, with 42% of the voters, but located far from the other cities
 Nashville on Wikipedia, with 26% of the voters, near the center of Tennessee
 Knoxville on Wikipedia, with 17% of the voters
 Chattanooga on Wikipedia, with 15% of the voters
The preferences of the voters would be divided like this:
42% of voters (close to Memphis) 
26% of voters (close to Nashville) 
15% of voters (close to Chattanooga) 
17% of voters (close to Knoxville) 





City  First  Second  Third  Fourth  Points 

Memphis  42  0  0  58  126 
Nashville  26  42  32  0  194 
Chattanooga  15  43  42  0  173 
Knoxville  17  15  26  42  107 
Nashville is the winner in this election, as it has the most points. Nashville also happens to be the Condorcet winner in this case. While the Borda count does not always select the Condorcet winner as the Borda Count winner, it always ranks the Condorcet winner above the Condorcet loser. No other positional method can guarantee such a relationship.
Potential for tactical voting
Like most voting methods, The Borda count is vulnerable to compromising. That is, voters can help avoid the election of a lesspreferred candidate by insincerely raising the position of a morepreferred candidate on their ballot.
The Borda count is also vulnerable to burying. That is, voters can help a morepreferred candidate by insincerely lowering the position of a lesspreferred candidate on their ballot.
For example, if there are two candidates whom a voter considers to be the most likely to win, the voter can maximize their impact on the contest between these candidates by ranking the candidate whom they like more in first place, and ranking the candidate whom they like less in last place. If neither candidate is their sincere first or last choice, the voter is employing both the compromising and burying strategies at once. If many voters employ such strategies, then the result will no longer reflect the sincere preferences of the electorate.
In response to the issue of strategic manipulation in the Borda count, M. de Borda said "My scheme is only intended for honest men."
Effect on factions and candidates
The Borda count is vulnerable to teaming: when more candidates run with similar ideologies, the probability of one of those candidates winning increases. Therefore, under the Borda count, it is to a faction's advantage to run as many candidates in that faction as they can, creating the opposite of the spoiler effect.
Criteria passed and failed
Voting systems are often compared using mathematicallydefined criteria. See voting system criterion for a list of such criteria.
The Borda count satisfies the monotonicity criterion, the summability criterion, the consistency criterion, the participation criterion, the Plurality criterion (trivially), Reversal symmetry, Intensity of Binary Independence and the Condorcet loser criterion.
It does not satisfy the Condorcet criterion, the Independence of irrelevant alternatives criterion, the Noncompulsory support criterion, or the Independence of Clones criterion.
The Borda count also does not satisfy the majority criterion, which means that if a majority of voters rank one candidate in first place, that candidate is not guaranteed to win. This could be considered a disadvantage for Borda count in political elections, but it also could be considered an advantage if the favorite of a slight majority is strongly disliked by most voters outside the majority, in which case the Borda winner could have a higher overall utility than the majority winner.
Donald G. Saari created a mathematical framework for evaluating positional methods in which he showed that Borda count has fewer opportunities for strategic voting than other positional methods, such as plurality voting or antiplurality voting, e.g.; "vote for two", "vote for three", etc.
Variants
 The Borda count method can be extended to include tiebreaking methods.
 Ballots that do not rank all the candidates can be allowed in three ways.
 One way to allow leaving candidates unranked is to leave the scores of each ranking unchanged and give unranked candidates 0 points. For example, if there are 10 candidates, and a voter votes for candidate A first and candidate B second, leaving everyone else unranked, candidate A receives 9 points, candidate B receives 8 points, and all other candidates receive 0. This, however, facilitates strategic voting in the form of bullet voting: voting only for one candidate and leaving every other candidate unranked. This variant makes a bullet vote more effective than a fullyranked vote. This variant would satisfy the Plurality criterion, the Favorite Betrayal criterion and the Noncompulsory support criterion.
 Another way, called the modified Borda count, is to assign the points up to k, where k is the number of candidates ranked on a ballot. For example, in the modified Borda count, a ballot that ranks candidate A first and candidate B second, leaving everyone else unranked, would give 2 points to A and 1 point to B. This variant would not satisfy the Plurality criterion, the Favorite Betrayal criterion, or the Noncompulsory support criterion.
 The third way is to employ a uniformly truncated ballot obliging the voter to rank a certain number of candidates, while not ranking the remainder, who all receive 0 points. This variant would satisfy the same criteria as the Borda count.
 A proportional election requires a different variant of the Borda count called the quota Borda system.
 A voting system based on the Borda count that allows for change only when it is compelling, is called the Borda fixed point system.
 A procedure for finding the Condorcet winner of a Borda count tally is called Nanson's method or Instant Borda runoff.
Current Uses of the Borda count
The Borda count is popular in determining awards for sports in the United States. It is used in determining the Most Valuable Player in Major League Baseball, by the Associated Press and United Press International to rank players in NCAA sports, and other contests. The Eurovision Song Contest also uses a positional voting method similar to the Borda count, with a different distribution of points. It is used for wine trophy judging by the Australian Society of Viticulture and Oenology. Borda count is used by the RoboCup robot competition at the Center for Computing Technologies, University of Bremen in Germany.
The Borda count has historical precedent in political usage as it was one of the voting methods employed in the Roman Senate beginning around the year 105. The Borda count is presently used for the election of ethnic minority members of parliament in Slovenia. In modified versions it is also used to elect members of parliament for the central Pacific island of Nauru and for the selection of Presidential election candidates from among members of parliament in neighbouring Kiribati. The Borda count and variations have been used in Northern Ireland for nonelectoral purposes, such as to achieve a consensus between participants including members of Sinn FÃƒÂ©in, the Ulster Unionists, and the political wing of the UDA.
In educational institutions, the Borda count is used at the University of Michigan College of Literature, Science and the Arts to elect the Student Government, to elect the Michigan Student Assembly for the university at large, at the University of Missouri GraduateProfessional Council to elect its officers, at the University of California Los Angeles Graduate Student Association to elect its officers, the Civil Liberties Union of Harvard University to elect its officers, at Southern Illinois University at Carbondale to elect officers to the Faculty Senate, and at Arizona State University to elect officers to the Department of Mathematics and Statistics assembly. Borda count is used to break ties for member elections of the faculty personnel committee of the School of Business Administration at the College of William and Mary. All these universities are located in the United States.
In professional societies, the Borda count is used to elect the Board of Governors of the International Society for Cryobiology, the management committee of Tempo sustainable design network, located in Cornwall, United Kingdom, and to elect members to Research Area Committees of the U.S. Wheat and Barley Scab Initiative.
Borda count is one of the feature selection methods used by the OpenGL Architecture Review Board.
Borda count is one of the voting methods used and advocated by the Florida affiliate of the American Patriot Party. See here and here.
See also
 List of democracy and electionsrelated topics
 Voting system  many other ways of voting
 Voting system criterion
 First Past the Post electoral system
 Instantrunoff voting
 Approval voting
 Plurality voting
 Condorcet method
 Schulze method
Further reading
 Chaotic Elections!, by Donald G. Saari (ISBN 0821828479), is a book that describes various voting systems using a mathematical model, and supports the use of the Borda count.
External links
 The de Borda Institute, Northern Ireland
 The Symmetry and Complexity of Elections Article by mathematician Donald G. Saari shows that the Borda Count has relatively few paradoxes compared to certain other voting methods.
 Article by Alexander Tabarrok and Lee Spector Would using the Borda Count in the U.S. 1860 presidential election have averted the american Civil War?
 Article by Benjamin Reilly Social Choice in the South Seas: Electoral Innovation and the Borda Count in the Pacific Island Countries.
 A Fourth Grade Experience Article by Donald G. Saari observing the choice intuition of young children.
 Consequences of Reversing Preferences An article by Donald G. Saari and Steven Barney.
 Rank Ordering Engineering Designs: Pairwise Comparison Charts and Borda Counts Article by Clive L. Dym, William H. Wood and Michael J. Scott.
 Arrow's Impossibility Theorem This is an article by Alexander Tabarrok on analysis of the Borda Count under Arrow's Theorem.
 Article by Daniel Eckert, Christian Klamler, and Johann MitlÃƒÂ¶hner On the superiority of the Borda rule in a distancebased perspective on Condorcet efficiency.
 On Asymptotic StrategyProofness of Classical Social Choice Rules An article by Arkadii Slinko.
 NonManipulable Domains for the Borda Count Article by Martin Barbie, Clemens Puppe, and Attila Tasnadi.
 Which scoring rule maximizes Condorcet Efficiency? Article by Davide P. Cervone, William V. Gehrlein, and William S. Zwicker.
 Scoring Rules on Dichotomous Preferences Article mathematically comparing the Borda count to Approval voting under specific conditions by Marc Vorsatz.
 Condorcet Efficiency: A Preference for Indifference Article by William V. Gehrlein and Fabrice Valognes.
 Cloning manipulation of the Borda rule An article by JÃƒÂ©rÃƒÂ´me Serais.
 Democracy and Social Choice: A Response to Saari Article by Mathias Risse.
 Cooperative phenomena in crystals and social choice theory Article by Thierry Marchant.
 A program to implement the Condorcet and Borda rules in a smalln election Article by Iain McLean and Neil Shephard.
 The Reasonableness of Independence Article by Iain McLean.
 Variants of the Borda Count Method for Combining Ranked Classifier Hypotheses Article by Merijn Van Erp and Lambert Schomaker
 Flash animation by Kathy Hays An example of how the Borda count is used to determine the Most Valuable Player in Major League Baseball.