Another (stronger) notion of what PR means would be: "Any subset of the voters (fraction F, all co-feeling) have the ability, by voting appropriately, to force victories for 'their' candidates, in total occupying at least a fraction F (up to reasonable error bound) of the seats."
What "appropriately" means, and what the "error bound" is, may differ. Most but perhaps not all of the PR methods I listed, also obey a theorem of this type. -- Warren D. Smith http://RangeVoting.org <-- add your endorsement (by clicking "endorse" as 1st step) and math.temple.edu/~wds/homepage/works.html ---- Election-Methods mailing list - see http://electorama.com/em for list info