[EM] SODA criteria

Kevin Venzke stepjak at yahoo.fr
Wed Feb 1 07:53:29 PST 2012

Hi Jameson,
I expect that unpredictability (whatever there may be) of candidates' decisions can only hurt criteria compliance.
At least with criteria that are generally defined on votes, because with such criteria you usually have to assume
the worst about any other influences incorporated into the method.
So I wonder, can you suggest a deterministic version of SODA, where the "negotiations" of SODA are instead
calculated directly from the pre-announced preferences of the candidates? And if so, does it satisfy the same
criteria in your view?
I can say I would be skeptical of how a criterion is being applied, or how clearly it is being defined, if the 
satisfaction of it *depends* on the fact that candidates have post-voting decisions to make.

De : Jameson Quinn <jameson.quinn at gmail.com>
À : EM <election-methods at lists.electorama.com> 
Envoyé le : Mardi 31 janvier 2012 20h50
Objet : [EM] SODA criteria

SODA passes: 

MMC (as voted)
Condorcet (as voted, and in a strong Nash equilibrium as honest)
Condorcet loser (ditto)
Participation (with the fix that delegation can be any fraction)
IIA (delegated version - that is, if a new candidate is added, the winner is either the same, or someone higher on the new candidate's delegation order.)
Polytime (there is no guarantee that optimal delegated assignment strategy is polytime calculable, but it will be in any real case, and anyway, candidates can just choose some near-optimal strategy.)
Allows equal rankings

So, of the criteria in the wikipedia voting systems table, the only ones it out-and-out fails are:
Consistency (though it comes damn close)
Later-no-harm and later-no-help (though it does satisfy LNHarm for the one (two????) candidate(s?) with the most voted approvals, and for other candidates, adding later preferences is probably strategically forced; so I'd say it fulfills the spirit of both of these. Similarly, it satisfies LNHelp for the last-to-delegate candidate, and nearly so for other late-delegating candidates, and the point of LNHelp is to prevent a weak candidate from winning through clever bottom filling, so again it satisfies the spirit.)
Allows later preferences (though delegation substitutes for this affordance in some cases.)

If we could just get some wikipedia-notable mention of SODA, we could put it in the table, and I think it would graphically stand out as the most criteria-compliant method there.

I'm working on an academic article on SODA, which would not be focused on these criteria or even on SODA, but would quickly state the above. But if anyone can make an article happen in a wikipedia "reliable source", that would be great.


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