[EM] IRV vs Condorcet
atarr at purdue.edu
Thu Jul 24 07:26:12 PDT 2003
Dave Ketchum wrote:
> Approval - actually more complex for the voter than ranked voting -
> all that is needed for rank is better vs worse, Approval requires
> judgment as to cutoff, but does not let the voter express the ranking
> required to get this far.
An interesting point - approval may be easy to understand HOW to vote in,
but voting intelligently is probably a little harder than in a good
> PR - debate this another day - for the moment I am staying with
> elections with single winners, and not concerned with legislatures where
> PR MIGHT make sense.
PR definitely makes sense. There's a lot of debate here about what sort of
PR is the best, but saying that means PR isn't a good idea would be like
saying plurality is good because we can't agree on the best alternative. I
know that's not what you're arguing about PR, but I'm just making the point.
> While IRV gets away from most of Plurality's spoiler problems, it
> has a few of its own. Condorcet simply DOES NOT DO spoilers.
While winning votes-based Condorcet lacks the conventional spoiler problem,
it is still definitely present in margins-based Condorcet. (Markus, here's
an example of a Condorcet supporter using a clones-type spoiler.)
Obviously Gore wins (save the jokes). Now add in Nader:
This example looks pretty similar to the eye to the ABC one you used, only
this one has the same spoiler as IRV when using margins-based
Condorcet. Winning votes Condorcet still gives the election to Gore by a
wide margin (sorry).
Furthermore, one of the tried-and-true criticisms that IRVists use against
Condorcet is "your second-pace vote can help defeat your first place
vote." This is virtually never true in winning votes, but it is frequently
true in margins. In the example above, if 2% of the Bush supporters
expressed a sincere second preference for Gore, they would cause Gore to
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