Approval voting

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Image:Approval ballot.svg Approval voting is a voting system used for elections, in which each voter can vote for as many or as few candidates as the voter chooses. It is typically used for single-winner elections, but can be extended to multiple winners. (However, multi-winner Approval voting does not return proportional results.) Approval voting is a limited form of range voting, where the range that voters are allowed to express is extremely constrained: accept or not.

It was advocated in 1968 and 1977 by Guy Ottewell. The term "Approval voting" was first coined by Robert J. Weber in 1976, but was fully devised in 1977 and published in 1978 by political scientist Steven Brams and mathematician Peter Fishburn. Historically, something resembling Approval voting for candidates was used in the Republic of Venice during the 13th century and for elections in 19th century England. Also the UN uses a process similar to Approval Voting to elect the Secretary General.

1 Procedures
2 Example
- 2.1 Potential for tactical voting
3 Effect on elections
4 Other issues and comparisons
- 4.1 Multiple winners
- 4.2 Relation to effectiveness of choices
5 Ballot types
6 See also
7 References
8 External links

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Procedures

Each voter may vote for as many options as he or she chooses, at most once per option. This is equivalent to saying that each voter may "approve" or "disapprove" each option by voting or not voting for it, and it's also equivalent to voting +1 or 0 in a range voting system.

The votes for each option are tallied. The option with the most votes wins.

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Example

Image:Tennessee map for voting example.svg

Imagine that the population of Tennessee, a state in the United States, is voting 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 live in one of these four cities, and that they would like the capital to be established as close to their city as possible.

The candidates for the capital are:

Memphis, the state's largest city, with 42% of the voters, but located far from the other cities
Nashville, with 26% of the voters
Knoxville, with 17% of the voters
Chattanooga, 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)
Memphis Nashville Chattanooga Knoxville	Nashville Chattanooga Knoxville Memphis	Chattanooga Knoxville Nashville Memphis	Knoxville Chattanooga Nashville Memphis

Supposing that voters voted for their two favorite candidates, the results would be as follows (a more sophisticated approach to voting is discussed below):

Memphis: 42 total votes
Nashville: 68 total votes (wins)
Chattanooga: 58 total votes
Knoxville: 32 total votes

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Potential for tactical voting

Approval voting passes the monotonicity criterion, in that voting for a candidate never lowers that candidate's chance of winning. Indeed, there is never a reason for a voter to tactically vote for a candidate X without voting for all candidates he or she prefers to candidate X. It is also never necessary for a voter to vote for a candidate liked less than X in order to elect X.

However, as approval voting does not offer a single method of expressing sincere preferences, but rather a plethora of them, voters are encouraged to analyze their fellow voters' preferences and use that information to decide which candidates to vote for. This feature of approval voting makes it difficult for theoreticians to predict how approval will play out in practice.

One possible tactic is that a voter will only approve of their first preference candidate; this will make it more difficult for other candidates to win. If every voter uses this tactic, then the election essentially turns into a first-past-the-post election, where the candidate with the largest plurality of first preference supporters wins.

One good tactic is to vote for every candidate the voter prefers to the leading candidate, and to also vote for the leading candidate if that candidate is preferred to the current second-place candidate. When all voters use this tactic, there is a good chance that the Condorcet winner will be elected. Approval voting fails to satisfy the Condorcet criterion. It is even possible that a Condorcet loser can be elected.

In the above election, if Chattanooga is perceived as the strongest challenger to Nashville, voters from Nashville will only vote for Nashville, because it is the leading candidate and they prefer no alternative to it. Voters from Chattanooga and Knoxville will withdraw their support from Nashville, the leading candidate, because they do not support it over Chattanooga. The new results would be:

Memphis: 42
Nashville: 68
Chattanooga: 32
Knoxville: 32

If, however, Memphis were perceived as the strongest challenger, voters from Memphis would withdraw their votes from Nashville, whereas voters from Chattanooga and Knoxville would support Nashville over Memphis. The results would then be:

Memphis: 42
Nashville: 58
Chattanooga: 32
Knoxville: 32

The mathematics of approval voting lend it to some manipulation and tactical voting. As each vote counts as one vote and the winner is the one with the highest total, each vote equally helps the candidate/issue (city in this example) selected win. Because of this, voters are more likely to only vote for their favorite. Because Approval voting has not been used much for real elections, this phenomenon is not well documented.

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Effect on elections

The effect of this system as an electoral reform measure is not without critics. Instant-runoff voting advocates like the Center for Voting and Democracy argue that Approval Voting would lead to the election of "lowest common denominator" candidates disliked by few, and liked by few, but this could also be seen as an inherent strength against demagoguery in favor of a discreet popularity. A study by Approval advocates Steven Brams and Dudley R. Herschbach published in Science in 2001<ref>Brams and Herschbach Template:Cite journal|journal=Science|volume=292|issue=5521|pages=1449|year=2001}}</ref> argued that approval voting was "fairer" than preference voting on a number of criteria. They claimed that a close analysis shows that the hesitation to support a lesser evil candidate to the same degree as one supports one's first choice actually outweighs the extra votes that such second choices get.

One study <ref>Results of experimental vote in france, 2002(PDF, French)</ref> showed that approval voting would not have chosen the same two winners as plurality voting (Chirac and Le Pen) in France's presidential election of 2002 (first round) - it instead would have chosen Chirac and Jospin. This seems a more reasonable result since Le Pen was a radical who lost to Chirac by an enormous margin in the second round.

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Other issues and comparisons

Advocates of approval voting often note that a single simple ballot can serve for single, multiple, or negative choices. It requires the voter to think carefully about who or what they really accept, rather than trusting a system of tallying or compromising by formal ranking or counting. Compromises happen but they are explicit, and chosen by the voter, not by the ballot counting. Some features of approval voting include:

Unlike Condorcet method, instant-runoff voting, and other methods that require ranking candidates, approval voting does not require significant changes in ballot design, voting procedures or equipment, and it is easier for voters to use and understand. This reduces problems with mismarked ballots, disputed results and recounts.
It provides less incentive for negative campaigning than many other systems, though the same incentive as instant runoff voting, condorcet method, and Borda count.
It allows voters to express tolerances but not preferences. Some political scientists consider this a major advantage, especially where acceptable choices are more important than popular choices.
Each voter may vote as many times as they wish, at most once per candidate. This is equivalent to saying that each voter may approve or disapprove each candidate by voting or not voting for them, and it's also equivalent to voting +1 or 0 in a range voting system.
It is easily reversed as disapproval voting where a choice is disavowed, as is already required in other measures in politics (e.g. representative recall).
In contentious elections with a super-majority of voters who prefer their favorite candidate vastly over all others, approval voting tends to revert to plurality voting. Some voters will support only their single favored candidate when they perceive the other candidates to be poor compromises.
Approval voting fails the majority criterion, so that the favorite candidate of a majority can fail to be elected.

However strategy issues of candidate list order if voters are not fully aware and reflective of the full set of candidates before any votes are cast.)

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Multiple winners

Approval voting can be extended to multiple winner elections, either as block approval voting, a simple variant on block voting where each voter can select an unlimited number of candidates and the candidates with the most approval votes win, or as proportional approval voting which seeks to maximise the overall satisfaction with the final result using approval voting. That first system has been called minisum to distinguish it from minimax, a system which uses approval ballots and aims to elect the slate of candidates that differs from the least-satisfied voter's ballot as little as possible.

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Relation to effectiveness of choices

Operations research has shown that the effectiveness of a policy and thereby a leader who sets several policies will be sigmoidally related to the level of approval associated with that policy or leader. There is an acceptance level below which effectiveness is very low and above which it is very high. More than one candidate may be in the effective region, or all candidates may be in the ineffective region. Approval voting attempts to ensure that the most-approved candidate is selected, maximizing the chance that the resulting policies will be effective.

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Ballot types

Approval ballots can be of at least four semi-distinct forms. The simplest form is a blank ballot where the names of supported candidates is written in by hand. A more structured ballot will list all the candidates and allow a mark or word to be made by each supported candidate. A more explicit structured ballot can list the candidates and give two choices by each. (Candidate list ballots can include spaces for write-in candidates as well.)

Image:Approvalballotname.png

Image:Approvalballotword.png

Image:Approvalballotmark.png

Image:Approvalballotchoice.png

All four ballots are interchangeable. The more structured ballots may aid voters in offering clear votes so they explicitly know all their choices. The Yes/No format can help to detect an "undervote" when a candidate is left unmarked, and allow the voter a second chance to confirm the ballot markings are correct.

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