[EM] Classifying 3-cand scenarios. LNHarm methods again.

[Dave Ketchum]

On Apr 18, 2010, at 11:08 AM, Kevin Venzke wrote:
> Hi Dave,
>
> --- En date de : Sam 17.4.10, Dave Ketchum  
> <davek at clarityconnect.com> a écrit :
>> Why IRV?  Have we not buried
>> that deep enough?  Why not Condorcet which does better
>> with about the same voting?
>
> In the context that I said I wanted to use IRV, I wanted to preserve
> LNHarm. It's kind of a moot point since I don't think it can be done.
> I would guess that certain Condorcet methods would do better than IRV
> in general, but in the symmetric scenario, it's not as clear to me  
> what
> specific behavior we need. It would be enough for me to have  
> incentives
> that keep the scenario from degrading to something simpler. I do think
> IRV would be adequate for that here.

If there is a CW, any Condorcet method is required to find it.  Else  
there is a cycle and we can debate over which such methods do better  
than others.

IRV, looking at the same ballots, cannot promise to find CWs, for its  
way of discarding potential winners without looking at complete  
ballots is its major failure.

I have to see little value in LNHarm.
      For A>B>C IRV will not see this voter's approving B and C over D  
until/unless seeing A lose.
      For this Condorcet will see all that this voter says of  B>C,  
B>D, and C>D.

For symmetric scenarios any Condorcet voter can vote any one or two  
sides of the triangle.   Net can be a CW or a cycle such as A>B>C>A.   
 From here, much simpler than sorting out what can be said to express  
this for Score.
>
>> Why TTR?  Shouldn't that be avoided if trying for a
>> good method?  TTR requires smart deciding as to which
>> candidates to vote on.
>
> I didn't really advocate TTR. The main thing that is nice about it is
> that there is plenty of room for three viable candidates and the  
> method
> is very simple.

If we are together, TTR is picking from what some other method, such  
as Plurality, saw as best two.  Trouble is either:
      They found the best one as such, and we might as well quit, or
      The other method did not include truly best two to hand to TTR.
>
>
> I don't think TTR voting strategy is a big problem. I'm more concerned
> about TTR nomination strategy.
>
>> Will not Condorcet attend to clones with minimum
>> pain?  Voters can rank them together (with equal or
>> adjacent ranks).
>
> The problem is that you have to get the voters to vote for those  
> clones.
> This is easier when there is no risk to doing so, and/or when they are
> allowed to do something to aid the clone set without having to vote  
> for
> all of them (such as votes against).

If the voters do not SEE clones, there is little to do for them.

If they DO see, they should be thankful for, and use, a method such as  
Condorcet that lets them rank such together.

"for all of them"?  Two is easy to have and to vote for; more would  
seem worth less effort due to less likelihood.
>
> I see Condorcet methods (the better ones) as a comprehensive solution
> that comes without a guarantee or much study about what it might
> accomplish. I know what I want to accomplish and I want to see if I  
> can
> find methods that will attend to that specifically. And perhaps more
> simply.
>
>> Does not Condorcet properly attend to "symmetric" with a
>> voted cycle?
>
> I responded to that above. It can, yes.
>
> Kevin Venzke