[EM] Condorcet methods - should the cycle order always determine the result order? CB

Thu Nov 6 16:50:35 PST 2014

Hi Chris,

"to the extent that the failures of these criteria are tolerable" means that certain extreme
candidate cloning issues shouldn't ultimately be problems in an assembly environment.
If a majority party has three candidates (and the members of this party support those candidates
to the extent that they would be willing to rank them together on a ballot) it should never
happen that the majority loses a vote (???) to a minority proposal. This does not mean that the
outcome was actually independent of the clones, just that a bizarre outcome should not result
from them.

And on the other side, a minority party can't possibly prevail in an assembly environment just
by making a large number of similar proposals.

The low value (that I perceive) of "total" clone independence is not just in the cost but in
what it actually gets you. That is, you only need one vote that denies that two candidates are 
clones, and suddenly clone independence guarantees no longer apply to this scenario. (Most 
serious clone-proof methods will still behave well, but it's trivial to define a method where
the usefulness of clone independence breaks down quickly given some noise. Like DSC, even.)

To me the cost is mostly simplicity, but also sometimes other criteria. I like C//A, which is
very simple but fails clone-winner. That doesn't really bother me. There's also ICA, which is
not so simple, but satisfies FBC. Clone-proof methods that satisfy FBC can't do much with
pairwise comparisons.

Kevin

----- Mail original -----
De : C.Benham <cbenham at adam.com.au>
À : election-methods at lists.electorama.com
Cc : 
Envoyé le : Jeudi 6 novembre 2014 8h10
Objet : Re: [EM] Condorcet methods - should the cycle order always determine the result order? (Toby Pereira)

Kevin,

You wrote:
> "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,..."

Can you can clarify your phrase "to the extent that the failures of 
these criteria are tolerable"?

What is it that we have to give up for  "total clone independence" that 
in your view makes it  "too expensive"?

Chris Benham

On 11/6/2014 1:20 PM, Kevin Venzke wrote:
> 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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