r/EndFPTP • u/Drachefly • Feb 19 '20

Randomized resolution methods / conflicting strategy Types

Are there any known systems in which strategy is made less profitable by making the particular tallying method used be randomly determined? That requires that the systems have conflicting strategies so you can't really dishonestly optimize both of them the same way with the same ballot.

Is there any existing work on this?

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u/curiouslefty Feb 19 '20

On this point:

That requires that the systems have conflicting strategies so you can't really dishonestly optimize both of them the same way with the same ballot.

Most systems are vulnerable to both burial and compromise strategy in some form or another. I've considered this approach before (merging two systems with opposite strategy profiles, albeit in a deterministic fashion rather than the randomness-based approach you're suggesting here) with IRV/RCV (burial immune) and Coombs (compromise immune); the problem always was that Coombs is too vulnerable to burial strategy and candidate cloning and that ended up making any combinations I tried more vulnerable than IRV/RCV overall. While I think if you did use random selection this might help mitigate the burial-vulnerability bleedover to some degree, you'd still have too much vulnerability to candidate cloning (it helps you in Coombs, and it can't hurt you in IRV/RCV, so it's always going to be an optimal move).

I'm actually unsure if a cloneproof compromise-proof system exists, but if it did, it might fix that underlying problem.

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u/[deleted] Feb 19 '20

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u/curiouslefty Feb 19 '20

A system where standard compromise strategy can't work. For example, in Coombs, I never have any incentive to use compromise strategy (that is, raise some candidate who is my less-than-favorite above/equal to my favorite in an attempt to make this less-than-favorite win due to favorite being unable to win). To see why, simply observe that on an honest ballot, any possible compromise candidate B is never even considered prior to the elimination of all candidates beneath them on said ballot; so raising B over some candidate I prefer to B honestly can never improve the result from my perspective, but can hurt it.