[EM] three-slot methods

[Kevin Venzke]

Forest,

 --- Forest Simmons <fsimmons at pcc.edu> a écrit : 
> Let's try your MAR method on the "unreliable poll" example that I consider
> to be Approval's achilles heel:

> Sincere votes would result in B and C surviving to the second round, with
> B, the sincere CW, winning.
> 
> This does seem to be better than MCA.

If only it were also as summable...  But it occurs to me that this idea:

> > once candidates
> > have majority approval, another measure is needed.  We could put a lot of things
> > here instead, such as electing the finalist with the most first-slot votes.

...which I might call "Majority Approval//First Preferences" ("MAFP") or something 
similar, could be done with the same information that MCA collects.  "If more than one 
candidate has majority support, elect the one with more first-place support."

The question with such a method is still: how often will it be useful to use the
middle rank?  I think it will still be useful in a lot of circumstances.  In your
first example, the first faction can vote A>B>C if they want to ensure that A
beats B in the second stage, and feel that that is more important than being able
to break B=C if those happen to be the finalists.  But if the A voters really doubt
that A will have a majority, they could conceivably up-rank B to first.  Not as
good.


Approval methods check low-utility candidates because of the risk involved in
approving them.  So trying to meet later-no-harm in general will just give us
something like Condorcet, I'm pretty sure.

So it seems the idea is that we want to meet later-no-harm when the "earlier"
preference (the "harmed" one) does "well enough."  That could mean majority
approval, majority favorite, or something else.  It would be very nice if we
could come up with such a rule that only *happened* to be majoritarian, and
was also functional in other cases.


Kevin Venzke
stepjak at yahoo.fr


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