[Election-Methods] RE : Corrected "strategy in Condorcet" section, Chris

[Kevin Venzke]

Chris,

> -------------------------------------------
> From: Chris Benham[SMTP:CHRISJBENHAM at OPTUSNET.COM.AU]
> Kevin Venzke wrote:
> 
> I think a better method that would achieve everything you are  
> trying to do with your method (technically
> if not "psychologically") would be this:
> 
> "1) Voters indicate one Favourite and also Approve as many  
> candidates as they like.
> 
> 2) Any candidate voted as favourite on 50% or more of the ballots  
> wins.
> 
> 3) Eliminate any candidate whose max. approval opposition score is  
> greater than 50%, unless that is all
> the candidates.  [I'm not sure if that's possible].
> 
> kv:
> Nope, that's not possible. You can only get this score if someone else
> has majority approval and you don't. It's an MD filter really.
>   
> 
> 4) Of the remaining candidates, the two voted as favourite on the  
> most ballots go to the second round."
> 
> This uses a more expressive ballot and mainly confines the split- 
> vote problem to the "top" of the ballot.
> So the normal recommended strategy in the 3 viable candidates  
> scenario would be vote the most preferred
> of the 3 as favourite, and approve all the candidates you prefer to  
> the least preferred of  the 3.
> 
> What do you think of that?
> 
> kv:
> I've had this exact thought... I agree that on paper this should be 
> similar in effect and better.
> 
> 
> Kevin,
> Thinking about this a bit more, why not expand this into a fully-fledged
> 3-slot method?
> 
> "Middle-slot votes count only as approval for calculating max. approval
> opposition scores.
> Candidates with a Max. AO score greater than 50% of the valid ballots are
> eliminated.
> Elect the remaining candidate with most top-slot votes."
> 
> I think that would be like a CDTT method. Wouldn't we then have a method
> that meets
> Minimal Defense, a variety of Later-no-Harm (middle-rating candidates
> can't harm the voter's top-rated
> candidates),FBC and  mono-raise; but fails Plurality,  3-slot Majority
> for Solid Coalitions, and Irrelevant Ballots,
> and has a sort of random-fill incentive?
> 
> What do you think of that? It seems so Venzke-like, have you ever
> proposed it? 

I don't know that I have proposed this method, but I have implemented
this method in my triangle plotter under the name "MD,FPP." I doubt
this method is as good as CDTT,FPP... Here are a couple of scenarios
where they differ:

39 A>C, 41 B>C, 20 C>B : MD,FPP picks B, CDTT,FPP picks C

In MD,FPP the A voters' compromise vote is less useful; also the C voters
would've gotten a C win if they had truncated.

49 A, 24 B>A, 27 C>B : MD,FPP picks A, CDTT,FPP picks B

Similar story here.

I would guess that MD,FPP is less vulnerable to offensive strategy...

Kevin Venzke


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