[Election-Methods] RE : Re: Is the Condorcet winner always the best?

[Dave Ketchum]

On Tue, 11 Dec 2007 12:20:49 -0800 Jonathan Lundell wrote:
> On Dec 11, 2007, at 6:05 AM, Kevin Venzke wrote:
> 
> 
>>Jonathan,
>>
>>--- Jonathan Lundell <jlundell at pobox.com> a écrit :
>>
>>>...should choose B as a good compromise, with the A voters saying A  
>>>is
>>>good, B OK, C very bad. But Diego's profile suggests to me that the A
>>>voters are saying something like A is good, B is bad, C is very bad.
>>>Not that they can express it in a normal linear ballot, just that
>>>we're being told a little more about their opinions.
>>
>>In my opinion, to the extent that the effect of a ">>bad>verybad"  
>>vote is
>>disregarded, the point of letting voters indicate such preferences is
>>undermined anyway.
> 
> 
> I'm not advocating it as a ballot option, only as a meta-notation  
> shorthand to give us kibitzers a little more information about the  
> voters' utility functions.
> 
> 
>>
>>>In my example, the effect of a later-no-harm voting rule is evident.
>>>In Diego's, a rule (such as STV) that elects A doesn't seem
>>>unreasonable to me.
>>>
>>>The problem is that with an ordinary linear ballot (no '>>'), we  
>>>can't
>>>distinguish between the cases. Not that I'm arguing that we should
>>>employ '>>'; offhand, that strikes me as a complication to be  
>>>avoided.
>>
>>In one sense I don't agree. If >> is allowed then apparently it's  
>>safe to
>>vote ">>bad>verybad." If >> isn't allowed then voters will probably  
>>be more
>>cautious, since the method could very well take them as serious if  
>>they say
>>that bad is better than verybad.
>>
>>I tend to think that if B doesn't win in Diego's scenario, the  
>>method is
>>second-guessing the voters. It either disbelieves the C voters'  
>>preference
>>for B over A, or finds that there's something more important than  
>>majority
>>rule.
> 
> 
> There's a reasonable argument to be made (hardly originally by me) on  
> either side of the question of whether a compromise candidate is  
> sometimes (or always) better to the candidate of one faction in a  
> close election.
> 
> If the vote were:
> 
> 53 A
> 47 C
> 
> ...we'd shrug and call it a fairly close election, or at least no  
> landslide, and forget about it, even if all 100 voters strongly  
> disapproved of the opposing candidate. If we introduce a third  
> candidate whom the A and C voters despise only slightly less than C  
> and A respectively, and end up with something like Diego's profile, we  
> have 100 (or 90 in that profile) unhappy voters instead of 47.

A and C agree that B is better than their standard enemy.

C voters will be happy to help install B, since this is better than 
installing A.  A voters may be a bit unhappy, but they at least avoided 
installing C.
> 
> I'm not saying that it's unarguable, nor that the voting system should  
> somehow anticipate the situation (through the use of '>>', for  
> example). I think it's a fuzzy case with no perfect answer, and that  
> we don't really want to make the ballot more complex, or add to the  
> possibilities for manipulation that such a rule would entail. I'm just  
> saying that it's not obvious that, in all cases, the best rule is the  
> one that lets B win.

Choices can be hard.  Get far enough from a tie and A or C will win.  If 
we manage a cycle we can debate the results of that.
-- 
  davek at clarityconnect.com    people.clarityconnect.com/webpages3/davek
  Dave Ketchum   108 Halstead Ave, Owego, NY  13827-1708   607-687-5026
            Do to no one what you would not want done to you.
                  If you want peace, work for justice.