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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