[EM] Condorcet for public proposals

[Kevin Venzke]

Anthony,

 --- Anthony Duff <anthony_duff at yahoo.com.au> a écrit : 
> I note that PC is not the simplest condorcet method.  PC means
> PC(winning votes).  PC(margins) would be simpler and more intuitive. 
> Margins are intuitive.  The pairwise contests are decided by margins.
>  The newcomer to condorcet will want to know why defeats should be
> used instead of margins.

I disagree on a couple of points.
1. I don't see how Margins is simpler.  When resolving scenarios with
pen and paper, Margins requires an extra subtraction step to find every
defeat strength.
2. I don't see why the margin, measured as the absolute number of votes
difference, is intuitive.  If anything, the relative margin seems more
intuitive; that is, a 14-2 contest would have strength of "7x," not 6.
3. Does the newcomer to Condorcet really want to know that?  Whenever
I introduce people to election methods, I don't bring up Margins very
early on, and I've yet to have it suggested to me.

I believe it is intuitive to measure defeat strength as the (absolute)
number of voters who can complain if the defeat is tossed out.

It might be more intuitive (in a different way) to measure defeat strength
as the number of non-abstaining voters (in that contest), but then voters
on the losing side might regret participating in the contest.  Also, we
need a secondary measure if all voters participate in certain contests.

> I wonder if, rather than explaining everything, an implicit “just
> trust me” approach would be better used in the first instance.  
> For example: 
> “When resolving a circular tie, measuring defeats by margins has been
> shown to be vulnerable to strategic manipulation.  By measuring
> defeats by winning votes, that vulnerability is significantly
> reduced”

I use examples which illustrate how WV works, and in passing note how
Margins would have differed.  I haven't yet found it necessary to discuss
differences in strategy, as whether or not Margins is more intuitive, it
doesn't seem to provide more intuitive *winners*.

>Has anyone got an argument for why a particular community might produce a
> sincere, circular tie?  Does anyone have evidence of one actually
> exisiting?

What is wrong with:
35 A>B
20 B
45 C ?

> I do not think the condorcet loser criterion is really that
> important.  The condorcet winner criterion is very important, and I
> might even rank it as paramount.  I think the symmetric relationship
> between these two criteria has artificially raised the status of the
> condorcet loser criterion.
> I think the condorcet loser criterion is less important than an 
> overruled majority.

I was recently considering a criterion to be called "Raynaud Loser,"
dictating that the method should not elect the loser of the strongest
pairwise contest.

If you care about not overruling majorities, strength has to be by WV.

> The prime example of PC electing a condorcet loser is:
> 20 ABCD
> 20 BCAD
> 20 CABD
> 13 DABC
> 13 DBCA
> 13 DCAB
> D wins despite being ranked last by 60% and despite being beaten by
> every other candidate.
> My justification of the win by D is this:  No other single candidate
> can stand up, in court or in public, and complain that they should be
> the winner because they beat D 60 to 39.  Should A, for example, do
> this, D can immediately counter by pointing out that A suffered a
> worse defeat of 66 to 33.  Therefore, A’s case is worse than D’s.
> Condorcet is a pairwise method.  Let the justifications and
> complaints be made in a pairwise manner.  I think this would be
> convincing in a public forum.

> Someone might suggest that A, B & C are effective clones, that they
> represent a similar position with respect to D.

This is what I see.

>  This is an advanced
> argument.  However, a problem with it is that the extreme strength of
> the cycle suggests that there are some very strong feelings
> differentiating A from B from C.  If they were clones, then why
> didn’t nearly as many vote CBA as ABC?

I'm afraid I don't find this very convincing, since each voter will know
whether they preferred the clones to D or vice versa.

> Another thought:  “condorcet” is an unfortunate name.  It is an
> unfamiliar French name.  People probably won’t even agree on how it
> is to be pronounced.  As for the abbreviation “PC” – it has already
> been used, as in “personal computer”, and in “politically correct”. 
> Are there any thoughts for a better name?

I like "pairwise methods."  For "PC" itself I prefer "MinMax."  But foremost
I would use the term "pairwise" to describe the method as different from
others.


Kevin Venzke
stepjak at yahoo.fr


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