Combined approval voting

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Combined approval voting (CAV) is an electoral system where each voter may express approval, disapproval, or indifference toward each candidate. [1] The winner is the most-approved candidate.

Contents

It is a cardinal system, a variation of score and approval voting, and is also known as dis&approval voting, [2] [3] balanced approval voting (BAV), [4] [5] approval with abstention option (AWAO), [6] true weight voting (TWV1), [7] [8] or evaluative voting (EV) [9] (though the latter can also be used for variants with more than 3 values.) It has also been called net approval voting [10] [11] [12] (though this term has a different definition in the context of approval-based committee selection). [13] [14]

Procedure

A ballot that treats blanks as abstentions, showing support for two candidates, opposition to two candidates, and abstention from one. Balanced Approval ballot.svg
A ballot that treats blanks as abstentions, showing support for two candidates, opposition to two candidates, and abstention from one.

Ballots contain a list of candidates, with 3 options next to each: "approve"/"disapprove"/"abstain", "for"/"against"/"neutral", or similar. [2] The ballot warns that blanks for a candidate are scored as "indifferent" votes. [2] Voters express their opinion of each candidate, and the votes are summed, with support = +1 and opposition = −1. The candidate with the largest score is the winner.

It's also possible to use ballots with 2 options, "approve"/"disapprove" and treat blanks as abstentions.[ citation needed ]

Unlike approval voting, in which non-approval could mean either disapproval or indifference, CAV allows explicit expression of disapproval, which is hoped to increase turnout, and reduce spoiled/blank ballots and insincere votes for unviable candidates. [2] Some jurisdictions allow a "none of the above" option to express disapproval of all candidates, but ballots that allow disapproval of specific candidates are otherwise rare. [2] [3]

History

CAV has been independently invented many times. It was originally proposed by Dan Felsenthal in 1989. [1] Claude Hillinger introduced the same concept in 2004 under the name "Evaluative Voting". [9] Alcantud and Laruelle gave it the name "Dis&approval voting" in 2012. [2] [15]

Properties

As this is mathematically equivalent to 3-level score voting, [16] it shares the same properties. For instance, it is always safe for a voter to approve their honest favorite (the favorite betrayal criterion). [9]

While a (-1, 0, +1) scale is mathematically identical to a (0, 1, 2) scale, there are psychological differences between the two, and the introduction of negative ratings (combined with the change in scoring blanks as middle grades rather than lowest grades) changes the scores that candidates receive in each system. Studies of French voters in 2012 found that, while the highest-rated candidate was the same under either system, and the grades of "exclusive" (polarizing) candidates were relatively unchanged, there were slight increases in the scores of "inclusive" (broadly-liked) candidates, and large increases in the scores of lesser-known candidates. [17]

Unlike other score voting scales, CAV is compatible with existing voting machines that can handle voting for/against ballot initiatives.[ citation needed ]

Related Research Articles

<span class="mw-page-title-main">Approval voting</span> Single-winner electoral system

Approval voting is an electoral system in which voters can select any number of candidates instead of selecting only one.

Score voting or range voting is an electoral system for single-seat elections, in which voters give each candidate a score, the scores are added, and the candidate with the highest total is elected. It has been described by various other names including evaluative voting, utilitarian voting, interval measure voting, point-sum voting, ratings summation, 0-99 voting, and average voting. It is a type of cardinal voting electoral system that aims to approximate the utilitarian social choice rule.

<span class="mw-page-title-main">Condorcet method</span> Pairwise-comparison electoral system

A Condorcet method is an election method that elects the candidate who wins a majority of the vote in every head-to-head election against each of the other candidates, whenever there is such a candidate. A candidate with this property, the pairwise champion or beats-all winner, is formally called the Condorcet winner. The head-to-head elections need not be done separately; a voter's choice within any given pair can be determined from the ranking.

<span class="mw-page-title-main">Voting</span> Method to make collective decisions

Voting is a method by which a group, such as a meeting or an electorate, convenes together for the purpose of making a collective decision or expressing an opinion usually following discussions, debates or election campaigns. Democracies elect holders of high office by voting. Residents of a jurisdiction represented by an elected official are called "constituents", and the constituents who choose to cast a ballot for their chosen candidate are called "voters." There are different systems for collecting votes, but while many of the systems used in decision-making can also be used as electoral systems, any which cater to proportional representation can only be used in elections.

<span class="mw-page-title-main">Copeland's method</span> Single-winner ranked vote system

Copeland's method, also called Llull's method or round-robin voting, is a ranked-choice voting system based on scoring pairwise wins and losses.

Disapproval voting is any electoral system that allows many voters to express formal disapproval simultaneously, in a system where they all share some power. Unlike most electoral systems, it requires that only negative measures or choices be presented to the voter or representative. If used to select candidates for an office, or for continuation to a next round of voting or play, it is either single- or multi-winner, as everyone who is not disapproved of is in effect a winner, for that round.

<span class="mw-page-title-main">Protest vote</span> Vote cast in an election as a form of political protest

A protest vote is a vote cast in an election to demonstrate dissatisfaction with the choice of candidates or the current political system. Protest voting takes a variety of forms and reflects numerous voter motivations, including political apathy. Where voting is compulsory, casting a blank vote is available for those who do not wish to choose a candidate, or to protest. Unlike abstention elsewhere, blank votes are counted.

"None of the above" (NOTA), or none for short, also known as "against all" or a "scratch" vote, is a ballot option in some jurisdictions or organizations, designed to allow the voter to indicate disapproval of the candidates in a voting system. It is based on the principle that consent requires the ability to withhold consent in an election, just as they can by voting "No" on ballot questions. It must be contrasted with "abstention", in which a voter does not cast a ballot.

In an election, a candidate is called a Condorcet, beats-all, or majority-rule winner if more than half of voters would support them in any one-on-one matchup with another candidate. Such a candidate is also called an undefeated, or tournament champion, by analogy with round-robin tournaments. Voting systems where a majority-rule winner will always win the election are said to satisfy the Condorcetcriterion. Condorcet voting methods extend majority rule to elections with more than one candidate.

Abstention is a term in election procedure for when a participant in a vote either does not go to vote or, in parliamentary procedure, is present during the vote but does not cast a ballot. Abstention must be contrasted with "blank vote", in which a voter casts a ballot willfully made invalid by marking it wrongly or by not marking anything at all. A "blank voter" has voted, although their vote may be considered a spoilt vote, depending on each legislation, while an abstaining voter has not voted. Both forms may or may not, depending on the circumstances, be considered to be a protest vote. Abstention is related to political apathy and low voter turnout.

The majority criterion is a voting system criterion. The criterion states that "if only one candidate is ranked first by a majority of voters, then that candidate must win."

In single-winner voting system theory, the Condorcet loser criterion (CLC) is a measure for differentiating voting systems. It implies the majority loser criterion but does not imply the Condorcet winner criterion.

<span class="mw-page-title-main">Rated voting</span> Electoral systems with independent candidate ratings

Rated voting refers to any electoral system which allows the voter to give each candidate an independent evaluation, typically a rating or grade. These are also referred to as cardinal, evaluative, or graded voting systems. Cardinal methods and ordinal methods are the two modern categories of voting systems.

<span class="mw-page-title-main">Ranked voting</span> Family of electoral systems

The term ranked voting, also known as preferential voting or ranked-choice voting, pertains to any voting system where voters indicate a rank to order candidates or options—in a sequence from first, second, third, and onwards—on their ballots. Ranked voting systems vary based on the ballot marking process, how preferences are tabulated and counted, the number of seats available for election, and whether voters are allowed to rank candidates equally.

Satisfaction approval voting (SAV), also known as equal and even cumulative voting, is an electoral system that is a form of multiwinner approval voting as well as a form of cumulative voting. In the academic literature, the rule was studied by Steven Brams and Marc Kilgour in 2010. In this system, voters may approve a number of candidates, and each approved candidate receives an equal fraction of the vote. For example, if a voter approves 4 candidates, then each candidate receives a 0.25 fractional vote. The election winners are those candidates that receive the highest fractional vote count.

Proportional approval voting (PAV) is a proportional electoral system for multiwinner elections. It is a multiwinner approval method that extends the highest averages method of apportionment commonly used to calculate apportionments for party-list proportional representation. However, PAV allows voters to support only the candidates they approve of, rather than being forced to approve or reject all candidates on a given party list.

<span class="mw-page-title-main">Sequential proportional approval voting</span> Multiple-winner electoral system

Sequential proportional approval voting (SPAV) or reweighted approval voting (RAV) is an electoral system that extends the concept of approval voting to a multiple winner election. It is a simplified version of proportional approval voting. It is a special case of Thiele's voting rules, proposed by Danish statistician Thorvald N. Thiele in the early 1900s. It was used in Sweden for a short period from 1909-1921, and was replaced by a cruder "party-list" style system as it was easier to calculate.

An approval ballot, also called an unordered ballot, is a ballot in which a voter may vote for any number of candidates simultaneously, rather than for just one candidate. Candidates that are selected in a voter's ballot are said to be approved by the voter; the other candidates are said to be disapproved or rejected. Approval ballots do not let the voters specify a preference-order among the candidates they approve; hence the name unordered. This is in contrast to ranked ballots, which are ordered. There are several electoral systems that use approval balloting; they differ in the way in which the election outcome is determined:

A major branch of social choice theory is devoted to the comparison of electoral systems, otherwise known as social choice functions. Viewed from the perspective of political science, electoral systems are rules for conducting elections and determining winners from the ballots cast. From the perspective of economics, mathematics, and philosophy, a social choice function is a mathematical function that determines how a society should make choices, given a collection of individual preferences.

The highest median voting rules are a class of graded voting rules where the candidate with the highest median rating.

References

  1. 1 2 Felsenthal, Dan S. (1989). "On combining approval with disapproval voting". Behavioral Science. 34 (1): 53–60. doi:10.1002/bs.3830340105. ISSN   0005-7940. k candidates ... each voter under CAV has k votes and can, with respect to each candidate, either cast one vote in favor of this candidate, or cast one vote against this candidate, or abstain from voting for this candidate. The outcome of a CAV ballot is the candidate with the largest net vote total (algebraic sum of votes in favor and votes against)
  2. 1 2 3 4 5 6 Alcantud, José Carlos R.; Laruelle, Annick (2013-09-06). "Dis&approval voting: a characterization". Social Choice and Welfare. 43 (1): 1–10. doi:10.1007/s00355-013-0766-7. hdl: 10366/127275 . ISSN   0176-1714. S2CID   253844191. The three levels have the following interpretation: 1 means approval, 0 means indifference, abstention or 'do not know', and -1 means disapproval. ... We investigate the 'dis&approval rule', that selects the candidates who obtain the largest difference between the number of positive votes and the number of negative votes.
  3. 1 2 "To approve or not to approve: this is not the question - Mapping Ignorance". Mapping Ignorance. Retrieved 2018-06-27.
  4. "Can Less be Better?". Negative Vote Association. 2018-01-22. Retrieved 2020-02-28. The sum is computed for each candidate and the winner is the candidate with the largest net vote.
  5. Cohen, Paul (2014-05-29). "Article: What Might be the Best Voting System?". OpEdNews. Archived from the original on 2018-06-16. Retrieved 2020-02-28. the votes For and Against each candidate are tallied and a net vote for each candidate is computed as the difference
  6. "Highlights of the Answers To Everything". AnswersToEverything. April 8, 2020. Retrieved 2020-04-11. Disapprovals are subtracted from approvals for each candidate, and candidate with highest margin of net-approval wins.
  7. Minet, Roy A. (2020-02-19). "Follow-on Election Simulation Leads to Definitive Proposal" (PDF). p. 3. TWV1 allows voters only three score values: -1, 0, and +1.
  8. Minet, Roy A. (2019-11-23). "Election Simulation Sheds New Light On Voting Methods" (PDF). p. 9. the Candidate having the highest positive (or least negative) total is the winner
  9. 1 2 3 Claude, Hillinger (2004-06-01). "Voting and the Cardinal Aggregation of Judgments". epub.ub.uni-muenchen.de. doi:10.5282/ubm/epub.353 . Retrieved 2018-06-27. The alternative that maximizes the sum wins. ... I argue for a three valued scale for general elections. ... with the scale (-1 (against), 0 (neutral), +1 (for)). In a committee of experts a more differentiated rule, EV-5, with the scale (-2,- 1,0,+1,+2) may be appropriate. ... A great advantage of EV is that the voter has no strategic incentive to withdraw his vote from the candidates he likes best.
  10. cestith (2018-06-08). "What is net approval voting?". Hacker News. Retrieved 2020-02-29. you vote up, down, or neutral on each candidate. The candidate with the most approvals minus specific disapprovals wins.
  11. "Demosthenes' Game: Perhaps a Way Out" . Retrieved 2020-02-29. Just two lines in the ballot: who you're for, and who you're against. The difference between 'for' and 'against' votes gives the candidate's net approval vote. Highest net approval vote wins.
  12. Kronos, Donald Arthur (2011-12-08). "An Easier Solution - A NET APPROVAL VOTING SYSTEM". Facebook. Retrieved 2020-02-29. able to indicate approval or disapproval of any number of candidates ... as additive votes to show approval and subtractive votes to show disapproval, where the candidate shown to have the highest net approval is the winner.
  13. Dey, Palash; Misra, Neeldhara; Narahari, Y. (2015-11-13). "On Choosing Committees Based on Approval Votes in the Presence of Outliers". arXiv: 1511.04190 [cs.MA].
  14. Faliszewski, Piotr; Slinko, Arkadii; Talmon, Nimrod (2017-11-17). "The Complexity of Multiwinner Voting Rules with Variable Number of Winners". arXiv: 1711.06641 [cs.GT].
  15. LARUELLE, Annick. "Research Project at the University of Cergy-Pontoise - Collective decision-making" (PDF).
  16. William., Poundstone (2008). Gaming the vote : why elections aren't fair (and what we can do about it) (1st ed.). New York: Hill and Wang. pp.  248. ISBN   9780809048939. OCLC   156818830. A three-valued system called "evaluative voting" has been proposed by D. S. Felsenthal, Claude Hillinger, and Mike Ossipoff. ... Mathematically, this is no different from allowing votes of 0, I, or 2.
  17. Baujard, Antoinette; Gavrel, Frédéric; Igersheim, Herrade; Laslier, Jean-François; Lebon, Isabelle (2018). "How voters use grade scales in evaluative voting". European Journal of Political Economy. 55: 14–28. doi:10.1016/j.ejpoleco.2017.09.006. ISSN   0176-2680.