[EM] RE : Re: A few concluding points about SFC, CC, method choice, etc.

[Juho]

On Feb 15, 2007, at 23:29 , Kevin Venzke wrote:

> --- Abd ul-Rahman Lomax <abd at lomaxdesign.com> a écrit :

>> Thus, we conclude, the Condorcet Criterion *must* be violated in some
>> elections by an optimal method, and thus this theoretical optimum
>> method must fail the criterion and others similar to it, such as the
>> Majority Criterion and SFC.
>
> I agree with this, although I don't think this theoretical optimum
> method exists. If it does exist I suppose it's pretty complicated.

I'm not ambitious enough to try to define a method that would give  
optimum results in all cases. Even proving this for one case is too  
difficult. I however think that it is a good practice to choose one  
utility function that the society agrees to approximate the real  
world needs accurately enough. There need not be one such function.  
Different targets may apply in different situations (one could seek  
best median utility or minimize worst utility to one individual,  
width of opposition, take into account strength of opposing opinions,  
strong first preference support to the winner etc.). And sometimes  
one the society may be satisfied with some other than the  
theoretically best utility function to make the system better in some  
other aspects (e.g. simplicity, strategy resistance).

>> Too often, when we consider methods by
>> election criteria, we assume that a criterion is desirable, entirely
>> apart from whether or not it chooses the optimum winner.
>
> I would guess that most of our criteria *do* coincide with higher
> utility. All things being equal you couldn't expect that a method that
> fails majority favorite would produce higher utility.
>
> There are other issues besides utility of course... There's the  
> question
> of what the public will accept and understand how to use, and there's
> all the questions of how to give the voter incentive to vote  
> sincerely.

Yes, all such criteria need to be considered. Abd ul-Rahman Lomax  
mentioned that also the majority rule could be violated. I agree that  
with some excellent utility functions that gives the best overall  
utility (e.g. Range style). One reason why the majority rule is  
popular is that it is hard to develop voting methods that would not  
respect it and still be strategy resistant. Or maybe majority rule is  
in some cases in line with the targeted utility function (e.g. to  
avoid a mutiny of the majority). (There are also other reasons, like  
simply the tradition.)

One reason why I think it would be good to always mention the target  
utility function is that then it is easier to compare the impact of  
the strategy resistance related modifications to some voting method  
against the basic utility function. It is typical that when strong  
anti-strategy measures are applied they make the achieved utility a  
bit worse. These two aspects, strategy resistance and good  
performance with sincere votes, need to be balanced. (I have often  
used the example of winning votes and ballots 49:A, 49:BC, 1:CA.)

Juho Laatu


		
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