[EM] MinMax Opposition

Kristofer Munsterhjelm km_elmet at t-online.de
Mon Nov 2 02:38:08 PST 2020

On 02/11/2020 06.51, John Karr wrote:
> I've seen very little written about the MinMax Pairwise Opposition
> Method. Which is surprising, given that it is the only Later Harm Safe
> RCV method other than IRV (that I'm aware of).
> It counts the votes against each choice and elects the choice that had
> the lowest opposition in its worst pairing.
> It appears to agree with Condorcet more often than IRV does and handle
> Clones much better than IRV. Its' weakness is that it fails the
> Plurality and Condorcet Loser Criterion.
> The obvious fixes involve pairing it with other methods such as
> restricting it to Smith Set when there is no Condorcet Winner (only
> helpful when there is no Condorcet Winner) or having a Runoff of the IRV
> Winner vs the MMPO winner, both of which introduce some later harm
> potential. Or alternately Dropping all choices lower in approval than
> the first choice votes for the plurality leader (while fixing Plurality
> it does not guarantee to eliminate the Condorcet loser) also introduces
> a later harm concern.

About the only thing MMPO has going for it is that it, indeed, meets
LNHarm and Participation. The cost is a very strong Plurality failure.
But if you try to fix the Plurality failure by modifying MMPO, then
it'll no longer meet either LNHarm or Participation. In that case, why
not use another method?

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