Bucklin voting: Difference between revisions
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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. |
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. |
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A [[majority]] is defined as being more half the number of voters. Since after the first round there are more votes cast than voters, it is possible for more than one candidate to have majority support. This makes Bucklin a variation of [[approval voting]]. |
A [[majority]] is defined as being more than half the number of voters. Since after the first round there are more votes cast than voters, it is possible for more than one candidate to have majority support. This makes Bucklin a variation of [[approval voting]]. |
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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. |
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. |
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Revision as of 22:48, 31 March 2008
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Bucklin voting is the name of a voting system that can be used for single-member and multi-member districts. It is named after its original promoter, James W. Bucklin of Grand Junction, Colorado and also known as the Grand Junction system.
Voting process
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 being more than half the number of voters. Since after the first round there are more votes cast than voters, it is possible for 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.
Usage
This method was used in many political elections in the United States in the early 20th century. In all states it was eventually repealed or, in two states, it was found to violate the state constitution. In Minnesota, it was the case of Brown v. Smallwood [1] which ended the use of Bucklin there, and in Oklahoma, the fractional votes involved in the peculiar application there were likewise found to be unconstitutional.[2]
Satisfied and failed criteria
Bucklin voting satisfies the majority criterion, the mutual majority criterion and the monotonicity criterion.
It fails the Condorcet criterion, independence of clones criterion, later-no-harm, participation, consistency, reversal symmetry, the Condorcet loser criterion and the independence of irrelevant alternatives criterion.
Example application
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 |
|---|---|---|---|
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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 Chattanooga 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 an 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.