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

[Chris Benham]

Kevin Venzke wrote:

>Chris,
>
>Chris writes [regarding NWL]:
>  
>
>>For a two-round method that is certainly something simple and "intuitive"
>>    
>>
>that improves on standard
>  
>
>>plurality TTR.  I assume the details are "in first round vote for oneas
>>    
>>
>favourite and approve as many 
>  
>
>>as you like. FPW wins with FP score of 50% or more. Otherwisequalifiers
>>    
>>
>are FPW and most approved
>  
>
>>alternative candidate. (Of course "favourite" also counts as"approved").
>>    
>>
>
>Actually, if I remember correctly I considered this to be a fully ranked
>method. You could specify more than one first preference.
>  
>
I was referring to the 2-round version (with relatively simple ballots). 
With these rules in a 2-round version
there would be no point in ballots that allow voters to do more than 
indicate first preference and approval.

In your single- round version with ballots that allow full ranking, are 
equal-first preferences split or whole?

>>For method that uses ranked ballots either in one round or in the firstof
>>    
>>
>two rounds, I prefer "elect the winner
>  
>
>>of the pairwise comparison between the IRV (Strict) winner and the Approval
>>    
>>
>winner".   That wouldn't have a
>  
>
>>clone problem, supporters of weak candidates would have no
>>    
>>
>"favourite betrayal" incentive, and it would meet
>  
>
>>Majority for Solid Coalitions and Dominant Mutual Third.
>>    
>>
>
>I wonder if this method doesn't have a similar problem as NWL.
>  
>
It probably does. In the 49A, 24B, 27C>B scenario the A supporters can 
shift the win from B to A by voting A>C
making C the AW. 

Chris Benham




>Chris,
>
>Chris writes [regarding NWL]:
>  
>
>>For a two-round method that is certainly something simple and "intuitive"
>>    
>>
>that improves on standard
>  
>
>>plurality TTR.  I assume the details are "in first round vote for one as
>>    
>>
>favourite and approve as many 
>  
>
>>as you like. FPW wins with FP score of 50% or more. Otherwise qualifiers
>>    
>>
>are FPW and most approved
>  
>
>>alternative candidate. (Of course "favourite" also counts as"approved").
>>    
>>
>
>Actually, if I remember correctly I considered this to be a fully ranked
>method. You could specify more than one first preference.
>
>And if the same candidate was the FPW and the AW then this candidate would
>win. Otherwise there seems to be a needless monotonicity problem.
>
>  
>
>>Of course in this method voters who are confidant that their favouritewill
>>    
>>
>be the FPW have a big incentive
>  
>
>>to approve all the turkeys and conversely voters who are confidant
>>    
>>
>thattheir favourite will be the AW might
>  
>
>>have incentive to vote a turkey as their favourite.But I doubt that
>>    
>>
>the risk of both qualifiers being turkeys is as
>  
>
>>great in approval top-2, and all this attempted "turkey raising" mighthelp
>>    
>>
>minor parties survive. :)
>
>That's something I wasn't thinking about back then, I guess. The ability
>of FPW supporters to approve turkeys seems too great. I'm not worried
>about AW supporters ranking turkeys as their favorite, though; this would
>run a substantial risk of giving the race to them.
>
>  
>
>>For method that uses ranked ballots either in one round or in the firstof
>>    
>>
>two rounds, I prefer "elect the winner
>  
>
>>of the pairwise comparison between the IRV (Strict) winner and theApproval
>>    
>>
>winner".   That wouldn't have a
>  
>
>>clone problem, supporters of weak candidates would have no
>>    
>>
>"favourite betrayal" incentive, and it would meet
>  
>
>>Majority for Solid Coalitions and Dominant Mutual Third.
>>    
>>
>
>I wonder if this method doesn't have a similar problem as NWL.
>
>
>  
>
>>>>... a potentially useful set:"the set of candidates whose approval score
>>>>        
>>>>
>is higher than  their  maximum approval opposition score".  
>  
>  
>
>>>I think it's pretty interesting... I'm having trouble thinking through
>>>these particular methods, but as a criterion it seems pretty good. Inote 
>>>that in the 7 5 8 plurality failure example, again B is required.It 
>>>reminds me of "pairwise plurality" (at least, my conception of it),where 
>>>a candidate can't win if their worst loss is stronger than theirbest win.
>>>      
>>>
> 
>
>  
>
>>Notice that in your NWL example
>> 
>>7 A>B5 B6 C2 D>C
>>the set is {B}, the winner by many of our preferred methods.  I invite you
>>to suggest a name for this set.
>>    
>>
>
>Well, in my mind this concept has more to do with "acknowledgment" than
>"approval." So I'd be more inclined to phrase it in terms of "voting for"
>a candidate than "approving" one.
>
>MD can be:
>"If >50% vote for X and don't vote for Y, then Y can't win."
>
>Plurality can be:
>"If there are more first preferences for X than votes for Y, then Y can't
>win."
>
>This would be:
>"If more people vote for X and don't vote for Y, than vote for Y, then
>Y can't win."
>
>I'm not sure what to call it... It's nice that it doesn't make reference
>either to a majority or to first preferences, though.
>
>Kevin Venzke
>
>
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>  
>
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