DeCondorcet is a name that may be used for any voting system satisfying Condorcet
's Criterion:
-
- Any candidate who is preferred by a majority of voters to each other candidate should win.
I am not aware of anywhere in the world where such a system is in use.
DebianGnuLinux uses DeCondorcet voting for their project leader and general resolution process.
For example, suppose
- 40 people vote ABC (i.e. they put A as their first choice, B as second, C as third)
- 10 vote BCA
- 10 vote BAC
- 40 vote CBA
Then B is preferred to A by a majority of 60 to 40, and to C by 60 to 40 as well. B was last on first preferences and would not win under
InstantRunoffVoting.
The big problem is that a candidate meeting the condition need not always exist. (If one always did,
ArrowsTheorem would be contradicted.)
For example, suppose
- 40 people vote ABC
- 30 vote BCA
- 30 vote CAB
This would suggest that a majority of 40 (70-30) prefer B to C, a majority of 20 prefer C to A and a majority of 40 prefer A to B. This situation is called a cycle.
Cycles are rare in practice, and can be resolved in a number of ways, suggesting that
DeCondorcet could be used for public elections. However opponents argue that
TacticalVoting can be used so as to create cycles and benefit from the cycle-breaker.
--
JoeOtten
Thanks a lot for the info. This does seem like a good
VotingMethodCriterion; surprising to me that
InstantRunoffVoting doesn't satisfy! --
BayleShanks
CategoryVoting