- Range voting
Range voting (also called ratings summation, average voting, cardinal ratings, score voting, 0–99 voting, or the score system or point system) is a
voting system for one-seat elections under which voters score each candidate, the scores are added up, and the candidate with the highest score wins. Range voting was used in all public elections in Ancient Sparta in the form of measuring how loud the crowd shouted for different candidates. Range voting with three levels was used in elections in Renaissance Venice, including when fewer than 50 voters cast ballots to elect the Doge between 1268 and 1797.Approval voting can be considered to be range voting with only 2 levels [approved (1) and disapproved (0)] .Voting system
Range voting uses a
ratings ballot ; that is, each voter rates each candidate with a number within a specified range, such as 0 to 99 or 1 to 5. Although incumulative voting voters are not permitted to provide scores for more than some number of candidates, in range voting all candidates can be and should be rated. The scores for each candidate are summed, and the candidate with the highest sum is the winner. If voters are explicitly allowed to "abstain" from rating certain candidates, as opposed to implicitly giving the lowest number of points to unrated candidates, then a candidate's score would be the "average" rating from voters who did rate this candidate.In some competitions subject to judges' scores, a
truncated mean is used to remove extreme scores. For example, range voting with truncated means is used in figure skating competitions to avoid the results of the third skater affecting the relative positions of two skaters who have already finished their performances (theindependence of irrelevant alternatives ), using truncation to mitigate biases of some judges who have ulterior motives to score some competitors too high or low.Another method of counting ratings ballots is to find the
median score of each candidate, and elect the candidate with the highest median score. This could have the effect of reducing the incentive to exaggerate. A potential disadvantage is that multiway exact ties for winner may become common, while in conventional range voting, such ties would be extremely rare. Another problem with medians is, e.g, that adding an "all-zero ballot"can alter the election winner.Range voting in which only two different votes may be submitted (0 and 1, for example) is equivalent to
approval voting . As with approval voting, range voters must weigh the adverse impact on their favorite candidate of ranking other candidates highly.Alternative use
The range voting concept has been used in non-political contexts also, Sports such as
gymnastics rate competitors on a numeric scale, although the fact that judges' ratings are public makes it less likely for them to engage in blatant tactical voting. Range voting is common for things where there is no single winner: for instance on the Web, sites allow users to rate items such as movies (Internet Movie Database ), comments, recipes, and many other things. Range voting is the primary voting method used and endorsed by theLibertarian Reform Caucus . cite web
url=http://reformthelp.org/issues/voting/range.php
title=Why alternative parties must get range voting, or die
accessdate=2007-10-09
last=Shentrup
first=Clay
authorlink=
coauthors=Warren D. Smith
publisher=Libertarian reform caucus]Range voting has been used informally by various amateur clubs to determine datesand venues for events like seasonal dinners. In one variant, any club member who wants to propose a date/time or restaurant writes it down on a whiteboard. All other members can each vote once for each new option; either by adding +1 to the total (in favour), casting no vote (neutral), or by subtracting one from the total (disapproval). At the end of the season, the club goes to the restaurant with the most votes, at the date and time with the most votes.fact|date=January 2008
Example
Suppose that voters each decided to grant from 1 to 10 points to each city such that their most liked choice got 10 points, and least liked choice got 0 points, with the intermediate choices getting an amount proportional to their relative distance.
Nashville, the capital in real life, likewise wins in the example.
Properties
Range voting allows voters to express preferences of varying strengths.
Range voting satisfies the
monotonicity criterion , i.e. raising your vote's score for a candidate can never hurt his chances of winning. Also, in range voting, casting a sincere vote can never result in a worse election winner (from your point of view) than if you had simply abstained from voting. Range voting passes thefavorite betrayal criterion , meaning that it never gives voters an incentive to rate their favorite candidate lower than a candidate they like less. Range voting advocates contend that this is a good property, because it leads to higher average voter satisfaction when voters are honest, and still gives voters the choice to strategically lower their scores for less preferred candidates if they choose.Range voting is independent of clones in the sense that if there is a set of candidates such that every voter gives the same rating to every candidate in this set, then the probability that the winner is in this set is independent of how many candidates are in the set.
In summary, range voting satisfies the
monotonicity criterion , thefavorite betrayal criterion , theparticipation criterion , theconsistency criterion ,independence of irrelevant alternatives ,resolvability criterion , andreversal symmetry . It is immune to cloning, except for the obvious specific case in which a candidate with clones ties, instead of achieving a unique win. It does not satisfy either theCondorcet criterion (i.e. is not aCondorcet method ) or theCondorcet loser criterion . It does not satisfy themajority criterion , but it satisfies a weakened form of it:a majority "can" force their choice to win, although they might not exercise thatcapability.As it satisfies the criteria of a deterministic voting system, with non-imposition, non-dictatorship, monotonicity, and independence of irrelevant alternatives, it may appear that it violates
Arrow's impossibility theorem . The reason that range voting is not regarded as a counter-example to Arrow's theorem is that it is a cardinal voting system, while Arrow's theorem is restricted to the processing of ordinal preferences. [cite journal|last=Arrow|first=Kenneth|authorlink=Kenneth Arrow|title=A Difficulty in the Concept of Social Welfare|journal=The Journal of Political Economy |volume=58|issue=4|date=August 1950|pages=328–346]trategy
In most cases, ideal range voting strategy for well-informed voters is identical to ideal
approval voting strategy, and a voter would want to give his least and most favorite candidates a minimum and a maximum score, respectively. If one candidate's backers engaged in this tactic and other candidates' backers cast sincere rankings for the full range of candidates, then the tactical voters would have a significant advantage over the rest of the electorate. When the population is large and there are two obvious and distinct front-runners, tactical voters seeking to maximize their influence on the result is to give a maximum rating to their preferred candidate, and a minimum rating to the other front-runner; these voters would then give minimum and maximum scores to all other candidates so as to maximize expected utility.However, there are examples in which voting maximum and minimum scores for all candidates is "not" optimal.cite web
url=http://rangevoting.org/RVstrat1.html
title=Examples in which best Range Voting strategy is not "approval style" voting
accessdate=
publisher=The center for range voting] Exit poll experiments have shown cite web
url=http://rangevoting.org/HonStrat.html
title=Honesty and Strategy in real-world voters
accessdate=
publisher=The center for range voting] that voters tend to vote more sincerely for candidates they perceive have no chance of winning. Thus range voting may yieldcite web
url=http://rangevoting.org/NurserySumm.html
title=The "Nursery Effect" (Executive summary)
accessdate=
publisher=The center for range voting] higher support for third party and independent candidates than other common voting methods, creating what has been called the "nursery effect", unless those candidates become viable.Because range voting produces lower Bayesian regret than other methodscite web
url=http://RangeVoting.org/BayRegDum.html
title=Bayesian regret for dummies
accessdate=
publisher=The center for range voting] , even when voters are strategic, many range voting advocates believe it is the most resistant voting method tostrategic voting .Advocacy
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