[EM] Majority-Judgement. Condorcet.

Kristofer Munsterhjelm km_elmet at lavabit.com
Sun Feb 5 13:59:21 PST 2012

On 02/04/2012 01:07 AM, Kevin Venzke wrote:
> Personally I don't understand why one would want to spend time on a
> method that you have to defend by saying "it might work anyway," even
> if as built the incentives are wrong.

I don't know if you're replying to me, but it seems to me that any 
deterministic rated method that satisfies two simple criteria would have 
an Approval vote as its maximally strategic vote, and voting 
strategically can't strictly be worse (for each individual voter) than 
not doing so.

The criteria are as follows:

- Per-candidate monotonicity: If you increase (decrease) the rating of 
candidate X, holding all other candidate scores constant, that will 
never reduce (increase) X's chance of winning.
- Per-candidate independence: Raising or lowering X's score while 
holding other scores constant never makes the winner turn from A to B 
(for some pair of other candidates {A, B}).

Range passes these. So does MJ.

By per-candidate monotonicity, increasing X's score to max will not hurt 
X. By per-candidate independence, doing so won't make a compromise 
candidate you might like lose, either.

So one may want to spend time on these methods because they're within a 
certain class of methods (those that pass the criteria above), even if 
that means that one can't help rewarding Approval-style ballots at least 
as much as honest ones. (MJ's big feature is then that in a way, it 
rewards Approval-style ballots as little as possible over honest ones. 
It does the best it can, given the constraints.)

> The name is so bad. Imagine you hear that on the news and are trying
> to figure out what it means. "Majority" doesn't tell you that much
> (IRV already does majorities and they didn't even need to put it in
> the name) and "judgment" refers to what? The voting. They're calling
> it "judgment" though. Puke. So dramatic and it doesn't even say
> anything.

"Majority" says that, unlike other rated methods, it passes Majority.
"Judgement" means that you're supposed to compare the candidates to an 
external grade standard (judge how good they are) instead of comparing 
them to each other.

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