Random Ballot
From Electowiki
Random Ballot, also known as Random Dictatorship, is a voting system in which the first preference candidate of a ballot drawn at random is elected.
When the drawn ballot is not decisive, then additional ballots are drawn and used only to resolve the indecision of previously drawn ballots.
[edit] Properties
Random Ballot satisfies the Plurality criterion, Monotonicity criterion, Participation criterion, Later-no-harm criterion, Clone Independence, Favorite Betrayal criterion, and Pareto criterion.
However, Random Ballot fails the Majority criterion, Condorcet criterion, Smith criterion, and Strong Defensive Strategy criterion.
[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)
|
Memphis wins with 42% probability, Nashville with 26%, Chattanooga 15%, and Knoxville 17%. If the Knoxville voters had instead ranked Knoxville and Chattanooga equally, then Knoxville would win with 0% probability, since it would be impossible to draw a ballot which prefers Knoxville to Chattanooga.
