Arrow's impossibility theorem: Difference between revisions
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(Rephrased to make more clear that normalization is not necessarily strategic, by moving strategic voting to a separate paragraph.) |
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==Statement== |
==Statement== |
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No [[Ordinal Voting]] system can be designed that always satisfies these three "fairness" criteria: |
No [[Ordinal Voting|ordinal voting]] system can be designed that always satisfies these three "fairness" criteria: |
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#[[Pareto Criterion]] |
#[[Pareto Criterion]] |
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#[[Independence of Irrelevant Alternatives]] |
#[[Independence of Irrelevant Alternatives]] |
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In addition, if the voters [[Strategic voting|vote strategically]], the first benefit is also lost. |
In addition, if the voters [[Strategic voting|vote strategically]], the first benefit is also lost. |
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===Caveats=== |
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Subsequent social choice theorists have expanded on Arrow's central insight, and applied his ideas more broadly. For example, the [[Gibbard-Satterthwaite theorem]] (published in 1973) holds that any deterministic process of collective decision making with multiple options will have some level of [[strategic voting]]. As a result of this much of the work of social choice theorists is to find out what types of [[strategic voting]] a system is susceptible to and the level of susceptibility for each. For example [[Single Member system | Single Member systems]] are not susceptible to [[Free riding]]. |
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==See also== |
==See also== |