[EM] IRV vs Condorcet vs Range/Score

[Aaron Armitage]

--- 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.
> 

Then we disagree about the importance of 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.
> 

This seems to be a typical complaint that Condorcet will elect a
compromise rather than a candidate that anyone is excited about. But if a
candidate people are excited about assumes office over the CW, then by
definition the majority is ruled against its will by an enthusiastic
minority. Even supposing that this majority is itself composed of
incompatible minorities does not mean that a polity whose electorate is
broken into several minority factions should just let one of those
factions govern. Wouldn't the acceptable compromise be fairer and more
stable?

If you're election the President of Iraq, do you really think the best
thing is for the Mandaean vote to decide (and probably not on the basis of
a particularly strong preference, FWIW) between the candidate who has the
Shi'a worked up and the candidate who has the Sunni worked up?

> 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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