Editing Talk:1844: Voting Systems
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:For reference: both instant run-off voting (IRV) and every concorcet method fail independence of irrelevant alternatives. Some (most?) condorcet systems satisfy all other criteria of Arrow's theorem, while IRV also fails monotonicity. Approval voting satisfies both, but it is outside the scope of Arrow's theorem as it is not a ranked voting system. [[User:Zmatt|Zmatt]] ([[User talk:Zmatt|talk]]) 18:47, 31 May 2017 (UTC) | :For reference: both instant run-off voting (IRV) and every concorcet method fail independence of irrelevant alternatives. Some (most?) condorcet systems satisfy all other criteria of Arrow's theorem, while IRV also fails monotonicity. Approval voting satisfies both, but it is outside the scope of Arrow's theorem as it is not a ranked voting system. [[User:Zmatt|Zmatt]] ([[User talk:Zmatt|talk]]) 18:47, 31 May 2017 (UTC) | ||
− | " | + | "Arrow's impossibility theorem states that when voters have three or more distinct alternatives (options), no ranked voting electoral system can convert the ranked preferences of individuals into a community-wide ranking." Arrow's theorem does not say that. Arrow's impossibility theorem says "When voters have three or more distinct alternatives (options), no ranked voting electoral system can convert the ranked preferences of individuals into a community-wide ranking that is <b>complete, transitive, Pareto efficient, have universal domain, has no dictator, and independent of irrelevant alternatives</b>." The conditions matter, and the non-dictatorship condition in particular is horrible misnamed.[[Special:Contributions/162.158.62.21|162.158.62.21]] 18:05, 31 May 2017 (UTC) |
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− | [[Special:Contributions/162.158.62.21|162.158.62.21]] 18:05, 31 May 2017 (UTC) | ||
:: Quite true. Monotonicity is not desirable because it enables the kind of strategies which make Condorcet systems almost as unstable in practice as FPTP. Arrow's Theorem can be disposed of by the realization that nonmonotonicity is what makes IRV impervious to strategy. [[Special:Contributions/162.158.6.46|162.158.6.46]] 07:16, 5 June 2017 (UTC) | :: Quite true. Monotonicity is not desirable because it enables the kind of strategies which make Condorcet systems almost as unstable in practice as FPTP. Arrow's Theorem can be disposed of by the realization that nonmonotonicity is what makes IRV impervious to strategy. [[Special:Contributions/162.158.6.46|162.158.6.46]] 07:16, 5 June 2017 (UTC) |