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Approval voting

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.

Table of contents
1 Procedures
2 An example
3 Potential for Tactical voting
4 Impact on elections
5 Other issues and comparisons
6 External Links


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

Imagine an election to choose the capital of Tennessee, a state in the United States that is over 500 miles east-to-west, and only 110 miles north-to-south. Let's say the candidates for the capital are Memphis (on the far west end), Nashville (in the center), Chattanooga (129 miles southeast of Nashville), and Knoxville (on the far east side, 114 miles northeast of Chattanooga). Here's the population breakdown by metro area (surrounding county):

Let's say that in the vote, the voters vote based on geographic proximity. Assuming that the population distribution of the rest of Tennesee follows from those population centers, one could easily envision an election where the percentages of sincere preferences would be as follows:

42% of voters (close to Memphis)
1. Memphis
2. Nashville
3. Chattanooga
4. Knoxville
26% of voters (close to Nashville)
1. Nashville
2. Chattanooga
3. Knoxville
4. Memphis
15% of voters (close to Chattanooga)
1. Chattanooga
2. Knoxville
3. Nashville
4. Memphis
17% of voters (close to Knoxville)
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):


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 she prefers to Candidate X.

However, as approval voting does not offer a single method of expressing her sincere preferences, but rather a plethora of them, the voter is encouraged to analyze her 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 she 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:

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:

Impact on elections

The impact 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:

External Links