Bucklin voting
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Bucklin is a voting system that can be used for single-member districts and also multi-member districts. It is also known as the Grand Junction system after Grand Junction, Colorado, where it was first proposed.
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How does it work?
Voters are allowed rank preference ballots (first, second, third, etc.).
First choice votes are first counted. If one candidate has a majority, that candidate wins. Otherwise the second choices are added to the first choices. Again, if a candidate with a majority vote is found, the winner is the candidate with the most votes in that round. Lower rankings are added as needed.
A majority is defined as half the number of voters, similar to Absolute majority. Since after the first round there are more votes cast than voters, it is possible more than one candidate to have majority support. This makes Bucklin a variation of approval voting.
For multi-member districts, voters mark as many first choices as there are seats to be filled. Voters mark the same number of second and further choices. In some localities, the voter was required to mark a full set of first choices for his or her ballot to be valid.
Where is it used?
This method was used in many political elections in the United States in the early 20th Century. In most states it was repealed and in a few states it was found to violate the state constitution.
Satisfied and failed criteria
Bucklin satisfies the majority criterion, the mutual majority criterion, monotonicity, and the strong defensive strategy criterion.
It fails the Condorcet criterion, clone independence, participation, consistency, the Condorcet loser criterion and the independence of irrelevant alternatives criterion.
An example
Imagine an election for the capital of Tennessee, a state in the United States that is over 500 miles (800 km) east-to-west, and only 110 miles (180 km) north-to-south. In this vote, the candidates for the capital are Memphis, Nashville, Chattanooga, and Knoxville. The population breakdown by metro area is as follows:
- Memphis: 826,330
- Nashville: 510,784
- Chattanooga: 285,536
- Knoxville: 335,749
If the voters cast their ballot based strictly on geographic proximity, the voters' sincere preferences might be as follows:
42% of voters (close to Memphis)
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26% of voters (close to Nashville)
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15% of voters (close to Chattanooga)
| 17% of voters (close to Knoxville)
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| City | Round 1 | Round 2 |
|---|---|---|
| Memphis | 42 | 42 |
| Nashville | 26 | 68 |
| Chattanooga | 15 | 58 |
| Knoxville | 17 | 32 |
The first round has no majority winner. Therefore the second rank votes are added. This moves Nashville and Chatanooga above 50%, so a winner can be determined. Since Nashville is supported by a higher majority (68% versus 58%), Nashville is the winner.
Voter strategy
Voters supporting a strong candidate have a advantage to "Bullet Vote" (Only offer one ranking), in hopes that other voters will add enough votes to help their candidate win. This strategy is most secure if the supported candidate appears likely to gain many second rank votes.
In the above example, Memphis voters have the most first place votes and might not offer a second preference in hopes of winning, but it fails because they are not a second favorite from competitors.
See also
- List of democracy and elections-related topics
- Voting system - many other ways of voting
- First Past the Post electoral system
- Instant-runoff voting
- Approval voting
- Borda count
- Majority-Choice Approval (a Bucklin variant)