[EM] Scoring (was Re: OpenSTV 2.1.0 released)

Juho Laatu juho4880 at yahoo.co.uk
Mon Sep 24 01:13:00 PDT 2012

On 24.9.2012, at 8.43, Michael Ossipoff wrote:

> You said that you don't support unimproved
> Condorcet. But then, later, maybe in the same post, you cited Dodgson
> and Beatpath as methods that you seem to be endorsing or advocating as
> methods that do better than SITC, with regard to the ideal sincere
> winner.

Unimproved Condorcet, as you defined it, may contain both good and bad methods. I don't support the bad ones. I have not taken position on Dodgson. I included Beatpath in what I referred to as "basic Condorcet methods". The only method that can be linked to my example sincere winner definition is Minmax(margins).

> But, as I explained in my previous post, you haven't told us what
> exactly you want in the way of an ideal sincere winner, or what method
> you think would choose it better than would SITC. (If you're sure you
> want to commit yourself to Dodgson or Beatpath, then say so
> unambiguously.)

I think I already said this a few times, but the idea is that the definition of which candidate should be elected with sincere votes can be election specific. I presented one possible definition. That definition happened to be the same as Minmax(margins). I don't claim that it is the best criterion for all elections, but it could be chosen for some.

> Nor did you answer my question about the chicken dilemma.

I answered something on the chicken dilemma. What more do you want to know?

> Basically, you haven't answered any of my questions.

I tried to cover all the questions in your mail. You may point out the unanswered ones, so I can check what I can do with them.

Btw, is this a promise that also you will answer all my questions?

>> But if you allow me to define the sincere winner for you, and for your >election, you could take my example definition and compare it to SITC.

>> There is a difference between those two definitions.
> What two definitions would those be?

SITC and the quoted lines below. I believe it is obvious that they are different.

>>>> (In my text above I asked you to provide a definition of the best candidate. A simple Condorcet oriented definition could be e.g. "the candidate that requires least additional support/votes to beat any of the other candidates in a pairwise comparison/battle should be elected". This target could be selected because it gives one rational argument why the winner could be able to rule well (= only little bit of additional support needed (if any) to gain majority support for his proposals while in office).)

> MinMax(margins) looks at the biggest defeat. Dodgson looks at the
> number of pairwise preferences that would have to be changed in order
> to make your candidate the CW. Those are two different considerations.
> You explicitly referred to the one that is Dodgson.

Check again. I didn't refer to changed votes but to least number of additional votes, which happens to be the same thing as biggest pairwise defeat in margins.

> Then you need next to show that Dodgson (or is it MinMax(margins)?) is
> indeed better than SITC, with regard to ideal sincere winner, "for
> some needs". Then you need to show that those needs are socially
> important and frequently needed.

No reference to SITC nor to Dodgson. But my quoted example best winner definition above includes also a short explanation on why this criterion might be considered useful for the society ("This target could be selected because..."). You can take that as a starter.

> But yes, if there's a top-cycle, the choice, under sincere voting, is
> less important, as compared to when there's a candidate who pairbeats
> each of the others.

I take that to mean that a complete definition of the best sincere winner should define also which candidate wins if there is a to loop.

> So you're now saying that Dodgson (the method you specified there)
> always chooses the ideal sincere winner.

The example definition (not Dodgson) could be used for some elections.

> For one thing, I claim that Dodgson is based on an illegitimate
> definition of "CW".

Ok, I have by now learned that you want to change the regular Condorcet criterion and interpretation of the rankings on the ballot to something else, and you consider that definition better, I guess both for defining the sincere winner and for practical elections.

> But you'd claimed that favorite-burial won't be a problem (but, when
> pressed, you become entirely vague about where it won't be a problem).

I can't exclude the possibility that some society would turn into widespread burial, but by default I assume that it is not a problem.


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