Voting System Criteria
Scholars rate voting systems using mathematically derived voting system criteria, which describe desirable features of a system. No ranked preference method can meet all of the criteria, because some of them are mutually exclusive, as shown by statements such as Arrow's impossibility theorem and the Gibbard-Satterthwaite theorem.
Many of the mathematical criteria by which voting systems are compared were formulated for voters with ordinal preferences. If voters vote according to the same ordinal preferences in both rounds, criteria can be applied to two-round systems of runoffs, and in that case, each of the criteria failed by IRV is also failed by the two-round system as they relate to automatic elimination of trailing candidates. Partial results exist for other models of voter behavior in the two-round system: see the two-round system article's criterion compliance section for more information.
The criteria that IRV meets, and those that it does not, are listed below.
Read more about this topic: Instant-runoff Voting
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—Tom Stoppard (b. 1937)
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—Hubert H. Humphrey (1911–1978)