[EM] Condorcet system, or Condorcet efficiency? (was:... wrt Burlington et al.)

[Jameson Quinn]

2011/11/29 robert bristow-johnson <rbj at audioimagination.com>
>
>
> IRV, with its kabuki dance of transferred votes, is more complicated than
> Condorcet.  when i was asked by one of the leaders in this town of the
> anti-IRV movement to explain Condorcet simply (since that was most of their
> case against IRV - most of their signs said "Keep Voting Simple"), i
> answered "If more voters agree that Candidate A is a better choice for
> office than Candidate B, then Candidate B is not elected."  pretty simple
> and hard to argue with.
>

This is a good description. However, it still conflicts with most people's
mental paradigm for how an election works, and so it seems more complex
than it is. Most people think an election is something like this:

1. People vote.
2. Those votes are translated into a score for each candidate.
3. The best score wins.

Plurality, Borda, Majority Judgment, Approval, and Range all fit that
paradigm. (That's why people are so prone to reinventing Borda.) Even IRV
and SODA can be shoehorned in, though it's a stretch. But Condorcet depends
on a matrix, not a list of scores; and that just doesn't fit inside
people's heads.

I'm not saying that this is a killer criticism of Condorcet. The other
advantages could easily outweigh this one disadvantage. But it is a factor.

>
> often the discussion here and that regarding Approval eventually discusses
> how voters can adapt their voting strategy to the method that is advocated
> for, and i continue to say that this misses the point.  the voters
> shouldn't have to be burdened with any need to strategize at all.  and they
> shouldn't be punished for failing to strategize.
>

I agree absolutely. That's why I think Range is not nearly as good as
Bayesian Regret would lead us to think. So, how much does each system
burden voters with the need to strategize, and how much does it punish them
for not strategizing?

Approval: It puts the strategic burden in your face; you can't avoid it.
But it doesn't actually punish you too much if you get it wrong. I expect
that a pile of low-knowledge approval votes is probabalistically the same
as some mixture (I'd guess around 50/50) of (A) well-strategized approval
votes with (B) honest range votes. That makes approval a pretty good
system, with a BR approaching Range but more resistance to one-sided
strategy.

Condorcet: Low strategic burden in the abstract. Unfortunately, because it
doesn't give nice, hard strategic guarantees, I think that people used to
plurality would over-strategize in Condorcet, and the system would not
necessarily react well.

Range: High strategic burden and high nonstrategic "penalty".

MJ: Guarantees that a strategic vote is semi-honest (as long as your
expectation for each candidate's scores are continuous and mutually
uncorrelated). Thus, though in the abstract the strategic burden/penalty is
about as bad as Condorcet, I think it would be easier to convince voters to
relax and just vote honestly.

SODA: Practically nonexistent strategic burden/penalty.

>
> while it is true that Condorcet may tend to favor the centrist (whereas
> IRV favors the largest subgroup in the largest group, e.g. in Burlington
> IRV favored the largest group, the Liberals, and of the Liberals, it
> favored the Progs over the Dems, because there was more Progs), it is no
> reason to adopt Condorcet.  the reason to adopt Condorcet is an argument of
> converse: if a CW exists and you elect any other candidate, the election
> has ignored the specific wishes of the majority of the electorate in
> rejecting the candidate they preferred more to the candidate the method
> elected.  there is no good reason to elect Candidate B to office when more
> of us have explicitly marked our ballots that we preferred Candidate A.


I believe that SODA in practice would elect more sincere, serious Condorcet
winners than a Condorcet system. ("Serious" means the ones who could
actually repeat their pairwise wins in a runoff with the same voters. In
other words, avoid the case of "I've never heard of this Pol Pot guy, but
he must be better than George Bush.") Condorcet systems do not necessarily
elect sincere Condorcet winners if the voters strategize.

Jameson
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.electorama.com/pipermail/election-methods-electorama.com/attachments/20111130/30030541/attachment-0003.htm>