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Approval voting

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Approval voting is a voting system used for single-winner elections, in which each voter can vote for as many or as few candidates as the voter chooses. 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 is used in the Elections for the Wikimedia Board of Trustees


Procedures

Each voter may vote for as many options as they wish, 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 them, and it's also equivalent to voting +1 or 0 in a range voting system.

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

An example

Tennessee and its four major cities: Memphis in the far west; Nashville in the center; Chattanooga in the east; and Knoxville in the far northeast

Suppose that Tennessee is holding an election on the location of its capital. The population is concentrated around four major cities. All voters want the capital to be as close to them as possible. The options are:

  • Memphis, the largest city, but far from the others (42% of voters)
  • Nashville, near the center of the state (26% of voters)
  • Chattanooga, somewhat east (15% of voters)
  • Knoxville, far to the northeast (17% of voters)

The preferences of each region's voters are:

42% of voters
Far-West 		26% of voters
Center 		15% of voters
Center-East 		17% of voters
Far-East
  1. Memphis
  2. Nashville
  3. Chattanooga
  4. Knoxville
  1. Nashville
  2. Chattanooga
  3. Knoxville
  4. Memphis
  1. Chattanooga
  2. Knoxville
  3. Nashville
  4. Memphis
  1. Knoxville
  2. Chattanooga
  3. Nashville
  4. 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
  • Chattanooga: 58 total votes
  • Knoxville: 32 total votes

Potential for Tactical voting

Approval voting passes a form of the monotonicity criterion, in that voting for a candidate never lowers their 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 prefers to Candidate X.

However, as approval voting does not offer a single method of expressing his sincere preferences, but rather a plethora of them, the voter is encouraged to analyze his fellow voters' preferences and use that information to decide which candidates to vote for.

A good strategy is to vote for every candidate the voter prefers to the leading candidate, and to also vote for the leading candidate if he is preferred to the current second-place candidate. When all voters follow this strategy, the Condorcet winner is almost certain to win.

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

Effect on elections

The effect of this system as an electoral reform is disputed. Instant-runoff voting advocates like the Center for Voting and Democracy argue that Approval Voting would lead to the election of "compromise candidates" disliked by few, and liked by few. A study by Approval advocates Steven Brams and Dudley R. Herschbach published in Science in 2000 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 'compromise candidate' to the same degree as one supports one's first choice (as approval voting requires) actually outweighs the extra votes that such second choices get. Accordingly, preference voting is more biased towards compromise candidates than approval voting - a non-obvious and surprising result. Citizens for Approval Voting was organized in December 2002 to promote the use of approval voting in all public single-winner elections.

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 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.
  • Increasing options for voters, when compared with the common First-past-the-post system, could increase voter turnout
  • It provides less incentive for negative campaigning than many other systems.
  • It allows voters to express tolerances but not preferences. This is considered by some political scientists 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).

Multiple winners

Approval voting can be extended to multiple winner elections, either as 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.

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 also include spaces for a write-in candidates as well)

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.

See also

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