[EM] Fw: IRV vs Condorcet vs Range/Score

[Aaron Armitage]

Chris Benham sent this to me. I think he meant to send it to the entire list; I've made the same mistake.

Reply to follow.


--- On Sun, 10/12/08, Chris Benham <cbenhamau at yahoo.com.au> wrote:

> From: Chris Benham <cbenhamau at yahoo.com.au>
> Subject: IRV vs Condorcet vs Range/Score
> To: "EM" <election-methods at lists.electorama.com>
> Cc: "Aaron Armytage" <eutychus_slept at yahoo.com>
> Date: Sunday, October 12, 2008, 11:01 AM
> Aaron,
> I agree that not electing a voted CW is undesirable, and
> any method
> that fails the Condorcet criterion needs to be justified by
> complying
> with at least one desirable criterion that isn't
> compatible with Condorcet.
> 
> "Low social utility (SU)" Condorcet winners with
> little solid support and
> depend for their status as the CW on weakly-held lower
> preferences can
> begin to look quite chimera-like and not necessarily the
> only legitimate
> winner.
> 
> One ok Condorcet method is Smith,IRV: voters strictly rank
> from the 
> top however many candidates they wish, before each normal
> IRV 
> elimination check for a candidate X that pairwise beats all
> the other 
> remaining candidates, elect the first such X to appear.
> 
> Is this what you mean by "Smith/IRV"? Or did you
> mean "Smith//IRV"?
> 
> I'm not sure if you suggested otherwise, but all
> methods that meet the
> Condorcet criterion are vulnerable to Burial strategy.
> 
> Chris Benham
> 
>  
> 
> Aaron Armitage wrote (Sat.Oct.11):
> Condorcet methods are the application of majority rule to
> elections which
> have more than two candidates and which cannot sequester
> the electorate
> for however many rounds it takes to produce a majority
> first-preference
> winner. If we consider majoritarianism an irreducible part
> of democracy,
> then any method which fails to elect the CW if one exists
> is unacceptable.
> 
> Which particular method is chosen depends on what you want
> it to do. For
> example, if we at to make it difficult to change the
> outcome with
> strategic voting Smith/IRV would be best, because most
> strategic voting
> will be burying a potential CW to create an artificial
> cycle in the hopes
> that a more-preferred candidate will be chosen by the
> completion method. A
> completion method which is also vulnerable to burial makes
> this worse, but
> Smith/IRV isn't because it breaks the cycle in a way
> the ignores all
> non-first rankings.
> 
> 
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