[EM] margins vs wv

[Elisabeth Varin/Stephane Rouillon]

Approval definitively favors centrists candidates.
As a voter I should be free to decide if I want to support one or more
candidates without the electing method affecting my winning probabilities.

So let us check another subject:
relative margins (rm) vs winning-votes (wv)

MIKE OSSIPOFF a écrit :

> A margins advocate could say that he doesn't consider the majority
> defensive strategy criteria important, but they measure for the
> standards of majority rule and getting rid of the lesser-of-2-evils
> problem. The wv methods are the ones that do well by the majority
> defensive strategy criteria. The wv versions of Ranked-Pairs and
> BeatpathWinner/CSSD meet all of them.

None of these criteria has shown to me that they can protect a Condorcet
Winner. It seems they show an enhancement of the probability of being able to
protect a Condorcet Winner and I like that. By how much are they efficient?

> Aside from whether you like those particular criteria, it can't really be
> denied that margins is the big
> violator of majority rule, and is the method that makes greater strategic
> demands on voters who want to protect majority rule, or who want to protect
> the win of a CW.

Please check  http://groups.yahoo.com/group/election-methods-list/message/10107
for an example where Winning Votes harms a Condorcet Winner.
So both criteria can harm a Condorcet Winner. The question is: how big is the
majority rule violation in both cases? Give me numbers from an A, B, C, AB, BC,
AC, BA, CB, CA distribution. I will do it myself, but for a small number of
voters. I sound like M. Carey, working with 3 candidates and 4 voters...

> It was shown here that, with margins methods, there are plausible
> ordinary situations in which the only Nash equilibria are ones in which
> defensive order-reversal is used.
>
> We probably agree that it's undesirable to have to drop a defeat,
> since each pairwise defeat represents a public vote about the
> relative merit of 2 candidates. Dropping a defeat overrules all the
> voters who won that public vote. So we'd like to at least overrule
> as few as possible.

Agreed. I even rallied to M. Tidemann's method consequence. It minimizes the
largest overruled pairwise comparison, so it minimizes the largest overruled
opinion created by different people. Another objective could be to minimize the
sum of overruled pairwise comparison, but it could count several times the
overuled occurence from a single individual. See
http://groups.yahoo.com/group/Electoral_systems_designers/message/77 for more
details.

> Margins advocates would answer that not dropping a defeat overrules
> the voters who voted agains that defeat. Wrong. Those voters were
> overruled by the result of the public vote between those candidates.
> Not dropping a defeat that the public enacted doesn't overrule anyone.

The same is valid for winning votes, no?

> For that reason winning-votes (wv) is the more democratic class of
> methods, when it comes to honoring pairwise votes and expressed
> public wishes.

Because I have not yet been able to quantify (wv) and (rm) Condorcets Winners
stilling probability, I cannot use this criteria to select the "most democratic
criteria". I prefer to use a quantifiable objective, the minimization of the
probability of overuling the wrong pairwise comparison, which is equivalent in
my sense to minimize the largest overuled relative margin.

> Margins advocates say that they like symmetry, and that margins
> is more symmetrical. But the situations isn't symmmetrical--If
> Smith beats Jones pairwise, there's an asymmetry between the Smith>Jones
> voters and the Jones>Smith voters: The Jones>Smith voters
> lost.

Not me.

Steph.

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