[Election-Methods] RELEASE: Instant Runoff Voting

[Chris Benham]

Aaron,
"In an important respect, Condorcet is more natural than IRV: if a majority prefers Brad over Carter, this preference exists whether the voting system does anything with it, or even elicits enough information to determine that it exists. "
Yes, except that "Condorcet" is a criterion and  IRV is a method, and  "more natural" doesn't have a precise meaning.

"Condorcet simply discovers and applies this preference. IRV, on the other hand, elicits enough information to discover it exists, but may decide to ignore it based purely on procedural grounds. There are no good reasons for this, ever."
IRV meets Later-no-Harm and  Later-no-Help and  is immune to Burial strategy, and these properties are incompatible with the Condorcet criterion.
Some people think these "reasons" are "good". 
""Core support" is a bogus reason: every time IRV chooses someone other than the plurality winner you're letting an overall majority trump a comparison of core supporters. But other times IRV will fail to do this, for reasons that simply don't exist apart from the system itself."
"Core support"  is  IMO just propaganda designed to reassure the public that IRV isn't  too radical a change from FPP.
BTW, which of the many methods that meet the Condorcet criterion is your favourite? 
Chris Benham


Aaron Armitage  wrote (Sun Jul 27,2008): 
Of course every reason you might offer for choosing one system over another is based on an idea of what a reasonable decision rule for making collective decisions in very large groups should look like. This is true for IRV advocate no less than advocates for other systems; where the system came from is beside the point, especially since most jurisdictions have never used the Exhaustive Ballot.

In an important respect, Condorcet is more natural than IRV: if a majority prefers Brad over Carter, this preference exists whether the voting system does anything with it, or even elicits enough information to determine that it exists. Condorcet simply discovers and applies this preference. IRV, on the other hand, elicits enough information to discover it exists, but may decide to ignore it based purely on procedural grounds. There are no good reasons for this, ever. "Core support" is a bogus reason: every time IRV chooses someone other than the plurality winner you're letting an overall majority trump a comparison of core supporters. But other times IRV will fail to do this, for reasons that simply don't exist apart from the system itself.


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