[EM] Query, Clones, MCA levels, Participation

[Kevin Venzke]

Forest,

 --- Forest Simmons <fsimmons at pcc.edu> a écrit : > 
> > Having said that, it occurs to me that the original, three-rank MCA is
> > not clone-proof if you interpret the MCA ballot as an ordinary ranked
> > ballot.
> 
> For these and other reasons I believe that it is better to base MCA/GB on
> CR style ballots.

Good idea, since MCA can be rephrased as three-level Median Rating.

What I've been wondering since my last post is whether there is a way to show
Clone Independence failures in methods where the voters are asked to rate, not
rank.  Both MCA and Approval's satisfaction of Clone Independence seem to depend
on the voting instructions.

I don't know off-hand of any rating methods which fail Clone Independence,
but it would be easy to come up with one.

The bigger question maybe is whether "Clone Independence" can be defined
in an unambiguous way that could apply to all types of methods.

> Here's an economical way to get a CR ballot with resolution sixteen:

Out of curiosity, do you think sixteen is not too many levels?  I think
even four is too many.  There would be three ways to win: Majority favorite,
greatest approval, and something in-between that we have difficulty
describing ("median at second-highest level").

Here's something I'll throw out there: The more ranks/levels MCA/Median has,
the more "drastically" it will fail Participation.  More generally, a method
should fail Participation more if it has multiple ways of winning, or if it
has multiple stages or rounds whose results affect later stages.

(As an example, I think Approval-Elimination Runoff should do better by
Participation than IRV, because the IRV elimination order is determined as
you go, whereas the "AER" elimination order is clear before anyone has been
eliminated.  This reduces your ability to mess up the elimination order to 
your detriment.)


Kevin Venzke
stepjak at yahoo.fr


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