[EM] Defensive strategy for Condorcet methods

[Juho Laatu]

On 15.6.2011, at 14.23, Kevin Venzke wrote:

> Hi Juho,
> 
> I have to trim this due to being short on time.

Thanks, compact opinions are always a good approach.

>>>> In margins (and maybe in other variants too) ties
>> should
>>>> not carry any other additional meaning but that
>> the voter
>>>> didn't support X>Y nor Y>X.
>>> 
>>> In a general context it is really unclear to me what
>> this means. It's
>>> like an IRV-oriented criterion that assumes you're
>> doing eliminations.
>>> It may be completely possible to satisfy you on this
>> point, and also 
>>> have a method that I don't find irritating. From what
>> you've literally
>>> written here I don't even see how it excludes WV.
>> 
>> There are maybe two ways to understand what the election
>> methods do. 1) Elect the candidate that is best according to
>> some (sincere) philosophy based on the given (hopefully)
>> sincere opinions of the voters. 2) Generate a set of
>> (whatever kind of) rules and let the voters cast their votes
>> in the best way they can to make the outcome best possible
>> for themselves. In the first approach we should have an
>> interpretation on what ranking two candidates equal means
>> from the utility and sincere preference point of view. If
>> the intended meaning of equal ranking is the same as
>> flipping a coin (and often it is about the same), then also
>> the results should be the same (in the first
>> interpretation). In the second interpretation any rules are
>> ok as long as other stated requirements are met (e.g. equal
>> treatment of all voters).
>> 
>> WV is not excluded even in the first interpretation if
>> there is a good explanation (that corresponds to some
>> "sincere" philosophy) to why pairwise defeat strengths are
>> measured the way WV does. It is quite natural to say that
>> the number of voters on the opposing side is an important
>> criterion (but may leave open the question does the number
>> of voters in favour of that candidate have some meaning as
>> well). I think the margins (sincere) philosophy is easier to
>> explain than the WV philosophy.
> 
> But with the first approach, with people being sincere, you shouldn't
> have to worry about equal ranking or truncation for the most part. Then
> WV and margins are the same.

In the first approach people *can* be sincere since the methods measures sincere opinions well enough, picks the winner based on the corresponding sincere philosophy, and is strategy free enough so that this sincere state of affairs will not break. I believe WV would be sufficient in real elections. It may well be strategy free enough for most needs. People may interpret equality as equality, and also equal last positions / truncation might not be considered strategic but sincere. Even if truncation would be generally interpreted as approval, still people might be happy with it and vote sincerely according to this philosophy. If WV some day would give somewhat strange results (like B winning with votes 49: A>B, 2: B>C, 49: C) people could accept also that since probably the votes would not be as extreme and simple and uniform as in the given example (probably people would call the result just "nearly a tie"). WV is thus not strategy free nor perfect otherwise but probably good enough to be able to live in the first category in most political elections.

Juho