[EM] Survey of Multiwinner Methods

[Jameson Quinn]

2013/1/7 Greg Nisbet <gregory.nisbet at gmail.com>

> Hey, I'd like to get a sense of what sorts of multiwinner methods are
> currently known that are reasonably good and don't require districts,
> parties, or candidates that are capable of making decisions (I'm looking at
> you, asset voting).
>

Like Abd, I wonder at the basis for your criteria. I think that for reform
in most English-speaking countries, districts are usually an advantage,
parties arguably so, and intelligent candidates always.

Also, this thread gives me an excuse to mention a thought I've recently
had. In between purely majoritarian methods and truly proportional ones,
there is a third option: median-preserving ones. That is, the legislature
is not proportional, but if the voters and candidates are on a 1D (or
N-dimensional single-peaked?) spectrum, then the median representative in
the winning set is the one closest to the median voter in the electorate.
The only example I've thought of so far is NP-complete (MJ ballots, each
voter has their individual threshold set as high as possible so that they
approve 1/2 of the winning slate) but I'm sure that there are other methods
which would do this. And such methods might have political advantages in
certain contexts.

Jameson

>
> I had an idea for a variant of STV where the "elimination order" for
> candidates is the reverse of how often they are approved (i.e. given a rank
> on the ballot instead of no rank). This method may already have been
> proposed some time ago, but I think it warrants attention regardless. This
> somewhat changes the interpretation of an STV ballot because a truncated
> ballot is no longer strictly less powerful than a non-truncated one. Since
> the elimination order is fixed from the beginning and doesn't depend on
> subsequent decisions, I suspect this modification to STV would at least
> reduce non-monotonic behavior (however one might quantify degree of
> monotonicity).
>
>
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