Correlated Instant Borda Runoff
From Electowiki
Correlated Instant Borda Runoff (CIBR) is a preferential voting system for single-winner elections, devised by Ken Kuhlman in May 2005 in order to reduce Borda's susceptability to clones.
[edit] Procedure
Candidates are scored according to the Borda count. The Borda loser of the most-correlated pair of candidates is eliminated. The process is repeated until only one candidate remains.
[edit] Example
Imagine an election for 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. 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)
|
26% of voters (close to Nashville)
|
15% of voters (close to Chattanooga)
| 17% of voters (close to Knoxville)
|
The Borda scores for the four candidates are:
- Nashville: 194
- Chattanooga: 173
- Memphis: 126
- Knoxville: 107
If "correlation" is defined as third-order correlation, then the most-correlated pair is Chattanooga and Knoxville. Knoxville has fewer Borda points and so is eliminated. After this elimination, the Borda scores for the remaining candidates are:
- Nashville: 126
- Chattanooga: 90
- Memphis: 84
and the correlations are:
- Nashville & Chattanooga: 100%
- Nashville & Memphis: 74%
- Chattanoogs & Memphis: 26%
The new most-correlated pair is Nashville and Chattanooga. Chattanooga is the Borda loser of this pair and is eliminated. The Borda scores of the remaining pair of candidates are:
- Nashville: 58
- Memphis: 42
Memphis is eliminated, and Nashville wins.
[edit] Criteria Compliance
CIBR passes:
It fails:
