On 4.6.2012, at 13.49, James Gilmour wrote: >>>> I think Plurality can be claimed to be the ideal method for the >>>> single-member districts of a two-party system, but then one should >>>> maybe also think that third parties should not be allowed to run, and >>>> we should stick to the same two parties forever. >>> >>> I don't get it. >>> >>> of course, if there are only two candidates, there is no problem with >>> Plurality (because it's also a Majority). >>> >>> so how is Plurality so flawed if we accept that a two-party system is >>> fine and dandy? if not Third parties, for Independents? >>> >>> what is the scenario with two parties where FPTP is so flawed? >> >> I think you already said it. If you want a system that allows >> also third parties and independents take part in the >> election, then Plurality is flawed. Only if you think that >> third parties and independents should nor run, and there >> should be only two parties, then Plurality is fine. > > These contributions to this discussion take an extremely narrow view of > representation of voters as it is clear this discussion is > not about a single-winner election (state governor, city mayor) but about > electing representative assemblies like state legislatures > and city councils. There can be major problems of representation if such > representative assemblies are elected by FPTP from > single-member districts even when there are only two parties. > > Even when the electorates of the single-member districts are as near equal as > possible and even when the turnouts are near equal, > FPTP in single-member districts can deliver highly unrepresentative results > if the support for the two parties is concentrated in > particular districts - as it is in most electorates. Thus party A that wins > 51 of the 100 seats in the assembly may win those > seats by small margins (say 550 votes to 450 votes) but party B that looses > the election with 49 of the 100 seats may have won its > seats by overwhelming margins (say 700 votes to 300 votes). Thus the 51 A to > 49 B result is highly unrepresentative of those who > actually voted: 42,750 for party A but 57,250 for party B. > > These numbers are deliberately exaggerated to show the point, but here in the > UK we see this effect in every UK General Election > since 1945, where the "win small, loose big" effect of FPTP has consistently > benefited the Labour Party at the expense of the > Conservative Party. > > And where such vote concentration exists - at is does everywhere - the > result can be greatly influenced by where the boundaries > of the single-member districts are drawn. "Move the boundary, change the > result". > > These are fundamental defects of FPTP in single-member districts that must be > addressed if you want your elected assemblies to be > properly representative of those who vote. > > Both of these defects has greater effect if the electorates are not so equal > or if the turnouts vary with party support (as they > certainly do in the UK). > > So even when there are only two parties, FPTP is very far from "fine". > > James Gilmour
Yes, that makes sense. FPTP in single-member districts is not fair in the sense that it gives only approximate results (due to the inaccuracy of counting the seats in single-member districts) and is vulnerable to gerrymandering. A system that counts the proportions at national level (typically a multi-party system) would be more accurate. Also gerrymandering can be avoided this way. The discussed proposal of changing the Plurality/FPTP method of the single-member districts to some other single-winner method has still many of the discussed problems (inaccuracy, gerrymandering). One could try to construct also two-party systems or single-member district based systems that would avoid those problems. But maybe proportional representation is a more likely "ideal end result". Practical reforms may however start with whatever achievable steps. Juho ---- Election-Methods mailing list - see http://electorama.com/em for list info