[EM] CD, briefer, better-workng, and with Juho's clarifications

Michael Ossipoff email9648742 at gmail.com
Sat Jan 11 06:26:55 PST 2014

I've added Juho's clarifications to CD's definition.

Additionally, I noticed that, not only didn't CD apply to Plurality, but it
didn't apply to Approval either, for the same reason. That wasn't
acceptable, when a criterion can't compare, to other methods, a method
widely agreed to be a contender for one of the best.

I'd felt that the premise stipulation that A would win under sincere voting
might not be necessary, but I was leaving it in because, it seemed
desirable. But when I found that it made the criterion apply to neiithr
Plurality nor Approval, I deleted that condition from the premise.

That was where it was necessary to speak of sincerity. Without that
stipulation, it's no longer for CD to speak sincerity or preferences. That
means that the sincere voting definition can be removed from the
Preliminary Definitions.

All this makes CD considerably briefer.

Now CD applies to Plurality. (Plurality doesn't pass), and to Approval.
Chicken Dilemma Criterion
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*Supporting definition:*

The A voters are the voters who vote A over everyone else. The B voters are
the voters who vote B over everyone else. The C voters are the voters who
vote C over everyone else.


1. There are 3 candidates: A, B, and C.

2. The A voters and the B voters, combined, add up to more than half of the
voters in the election.

3. The A voters are more numerous than the B voters. The C voters are more
numerous than the A voters, and more numerous than the B voters.

4. The A voters vote B over C. The B voters refuse to vote A over anyone.

5. None of the C voters vote A or B over the other.


B doesn't win.

[end of CD definition]


In the chicken dilemma scenario described in the premise of the Chicken
Dilemma Criterion (CD) defined above, if B won, then the B voters would
have successfully taken advantage of the A voters' co-operativeness. The A
voters wanted to vote both A and B over the candidates disliked by both the
A voters and B voters. Thereby they helped {A,B} against worse candidates.
But, with methods that fail CD, the message is "You help, you lose".

*Some methods that pass the Chicken Dilemma Criterion:*

ICT, Symmetrical ICT
MDDTR, IRV <http://wiki.electorama.com/wiki/IRV>, Benham's
Woodall's method <http://wiki.electorama.com/wiki/Woodall%27s_method>
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