[EM] proportional constraints - help needed

[Juho Laatu]

On 12.2.2013, at 1.24, Jameson Quinn wrote:

> 2013/2/11 Kristofer Munsterhjelm <km_elmet at lavabit.com>

> (Also, speaking of criteria: if I had enough time, I would try to find a monotone variant of Schulze STV. I think one can make monotone Droop-proportional multiwinner methods, since I made a Bucklin hack that seemed to be both monotone and Droop-proportional. However, I have no mathematical proof that the method obeys both criteria.)
> 
> What does monotone even mean for PR? You can make something that's sequentially monotone, but it's (I think) impossible to avoid situations where AB were winning but changing C>A>B to A>B>C causes B to lose (or variants of this kind of problem). That's still technically "monotone", but from a voters perspective, it's not usefully so.

I think monotonicity is sometimes an obvious requirement but not always. A ranked ordering (=> monotonicity with respect to adding seats) may give different results than a proportional algorithm that just picks the agreed number of representatives (with no order). Sometimes a ranked ordering is needed (like in the Czech Green Party canddidate list), sometimes not. The need to establish a ranked order may make the proportionality of the results slightly worse.

I also like the Alabama paradox in the sense that one can as well consider such results the correct and exact outcome, not a "negative paradox". All in all, both appraches are needed, for different needs.

Juho



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