Independence of irrelevant alternatives: Difference between revisions
Independence of irrelevant alternatives (view source)
Revision as of 18:26, 19 May 2024
, 1 month agoAdded behavioral IIA failure and way to avoid it, and linkified LIIA
(IIA implication: added Warren Smith reference, and panel data references from Wikipedia. Clarified how min-max is an adjustment of the voter's voting scale.) |
(Added behavioral IIA failure and way to avoid it, and linkified LIIA) |
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* '''[[Independence of covered alternatives]]'''
* '''[[Independence of Pareto-dominated alternatives]]''' (IPDA)
* '''[[Local independence of irrelevant alternatives]]''' (LIIA), which says that if the alternative ranked first or last in the outcome is removed, the relative ordering of the other alternatives in the outcome must not change.
* Woodall's '''Weak IIA''': If we add a new alternative y (who is ahead of x on some ballots) on which x was first preference (and nowhere else), then either x or y should be elected.
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=== Strategic implications ===
Voting systems which are not independent of irrelevant alternatives suffer from [[strategic nomination]] considerations.
==Related effects==
I.J. Good and [[Nicolaus Tideman]] argued that voters who can't tell close enough candidates apart may change their ranking or rating of candidates when unrelated candidates enter the race. The unrelated candidates work as reference points, allowing the voter to tell otherwise indiscernible candidates apart.<ref name="m085">{{cite journal | last=Good | first=I. J. | last2=Tideman | first2=T.N. | title=C93. The relevance of imaginary alternatives | journal=Journal of Statistical Computation and Simulation | volume=12 | issue=3-4 | date=1981 | issn=0094-9655 | doi=10.1080/00949658108810466 | pages=313–315}}</ref> As pointed out in the paper, this apparent "IIA failure" can be eliminated if the voters pretend that such reference point candidates exist even when they're not actually running.
==See also==
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