[EM] Fwd: Coombs. Elimination Examination.

Kristofer Munsterhjelm km_elmet at t-online.de
Wed Sep 27 06:52:00 PDT 2023

On 9/25/23 20:41, Michael Ossipoff wrote:

> Some academic authors have high praise for Coombs. One say that, with 
> sincere ranking, & fewer than 5 candidates, Coombs always elects the CW.

That can't be right:

1: A>C>B>D
1: B>C>A>D
2: A>D>B>C
1: A>C>D>B
3: B>C>D>A
1: D>A>C>B

A is the CW but has highest last preference count and so is eliminated 

However, it *is* true for three candidates.

> But Coombs is obviously vulnerable to east burial strategy. In 
> particular, trust & betrayal perpetrated by the voters of a “ lesser”-evil.

Clearly then, knowing this fact, the voters who propose and enact Coombs 
must be tough voters who would never ever bury. Therefore Coombs' burial 
incentive is no problem wherever it would be proposed.

I jest :-)

My real point is "beware arguments that are too powerful; they might 
just lead to absurdity".

Amusingly, according to James Green-Armytage, if we don't care about 
strategic susceptibility, then Coombs has a better VSE than IRV. So if 
we can simply discard strategy by the (too general) argument that 
strategy will never come into play, it's Coombs, not IRV, that ought to 
be enacted.


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