[EM] Condorcet methods - should the cycle order always determine the result order? (Toby Pereira)

Kevin Venzke stepjak at yahoo.fr
Wed Nov 5 18:50:06 PST 2014


Hi,
________________________________
>De : Kristofer Munsterhjelm <km_elmet at t-online.de>
>À : Toby Pereira <tdp201b at yahoo.co.uk>; Forest Simmons <fsimmons at pcc.edu>; EM <election-methods at lists.electorama.com> 
>Envoyé le : Mercredi 5 novembre 2014 15h29
>Objet : Re: [EM] Condorcet methods - should the cycle order always determine the result order? (Toby Pereira)
>
>On 11/05/2014 09:54 PM, Toby Pereira wrote:
>
>> But this also makes me wonder generally - are there any sensible
>> cloneproof ranked-ballot systems that aren't Condorcet methods? IRV is
>> cloneproof, but is it sensible? Is there anything else?
>
>Perhaps one of the descending coalitions family? DAC, DSC or HDSC. 
>They're cloneproof, but to determine whether they're sensible, you'd 
>probably need a more exact definition of what "sensible" means. They're 
>a lot closer to Plurality than Condorcet is.

Yes, I think those are probably the most fitting suggestions even if they're not that
great. I plotted methods based on similarity some time ago:
http://permalink.gmane.org/gmane.politics.election-methods/18829

........................Bucklin............................. 
............................................................ 
............................................................ 
..............................DAC........................... 
...................WV....................................... 
............................................................ 
............................BklnVar......................... 
..............C//KH......................................... 
............................................................ 
.............KH............................................. 
.................C//IRV..................................... 
.......................QR................................... 
...................................DSC...................... 
..................IRV....................................... 
.......................................FPP..................

Methods on the east side (DAC/DSC) don't seem to get invented very often. You probably
won't get much more unusual than these without failing the Plurality criterion.

My own basic principle for sensibility is that the winner of the election should be
one of those candidates who might be the winner if the electorate had been an assembly,
capable of surveying how many voters were available to vote in any given way, and 
adjusting votes based on which outcomes might actually be achieved. I think of other
candidates (i.e. those who could not plausibly have won in an assembly setting) as
"unrealistic" winners.

I think that this principle almost implies Condorcet (some worthwhile edge cases might
exist I think), and I think it implies clone-winner and clone-loser to the extent that
the failures of these criteria are tolerable.

Total clone independence is too expensive for me to insist on, and in itself doesn't
even reassure me that there won't be "clone-like" issues. The definition of "clone"
is very strict.

Kevin



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