[EM] IRV-Approval, Condorcet-Approval hybrids

[Kevin Venzke]

David's method gives me a similar, simpler idea that would seem to be an
improvement over IRV.  The method would be:

1. The voters rank the candidates they would be willing to support, and also
place an approval cutoff.  (Alternatively, all candidates ranked non-last
could be considered "approved.")
2. While there is no (voted) majority favorite, eliminate the Approval loser.
3. Elect the voted majority favorite.

Actually, I think this is Chris Benham's idea, suggested as a solution to the
strong FBC problem.  At the time I thought it would always elect the Approval
winner, but that's clearly wrong.  An example, where all ranked candidates are 
considered approved:

20: C>A
35: A>B
45: B

B is the Approval winner, but A is a majority favorite once C is eliminated.

A problem with this method, as well as with IRV and David's method (I am pretty
sure), is the incentive to up-rank compromises in attempt to achieve a majority
earlier.

The method wouldn't necessarily elect a CW, but I suspect it would fail to do
so for the same reasons Approval may: In the "weak centrist" scenario, for
instance, a major faction can't support the centrist and also hope to elect
their favorite, so the centrist's value has to be considered.  (Condorcet in
comparison allows the faction to do both.)

One thing I like about this IRV variant is that it seems to better represent an
actual decision-making process that might occur if all the voters were able to
get together, discuss, and shift support dynamically.  It seems a reasonable
principle that, if no option has a majority, the option with the least enthusiasm
(approval) is withdrawn.


This leads me to the other topic.  The most "common" Condorcet-Approval hybrid,
it seems to me, is to elect the Approval winner among the Smith set members.
I've read that there is concern about strategy incentives under those rules.
I wonder if that concern could be lessened if the rule were instead:

While there is no CW,
  Eliminate the Approval loser.

This will always elect a Smith set member, because it's not possible to
eliminate all Smith set members without creating a CW.

This seems better, to me, than Smith//Approval, because it still uses the
pairwise contests to make a decision.  The Approval winner won't necessarily
win.

Any thoughts...?


Kevin Venzke
stepjak at yahoo.fr


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