[EM] Election-Methods Digest, Vol 62, Issue 10 - Explaining PR-STV

[James Gilmour]

I have changed the subject to make it clear and to link it again to the related posts  - apologies for not doing that on my previous
post.

What you describe below is not a feature of the SNTV voting system but the careful strategic and tactical manipulation of the voting
system to obtain a PR outcome.  But even then, it is only PR of the registered political parties.  Iif the voters expressed their
true wishes about the candidates, PR of the parties would probably not be obtained.

So I think my statement was a fair one.

James


Kristofer Munsterhjelm > Sent: Monday, August 31, 2009 7:17 AM
> James Gilmour wrote:
> > It is extremely important to refer to STV as the SINGLE Transferable 
> > Vote, because each voter must have only one vote to ensure PR. This 
> > distinguishes STV from all multiple vote systems, like 
> > Multi-Member-FPTP or the Cumulative Vote.  It is also important to 
> > emphasise the Single TRANSFERABLE Vote, because PR cannot be obtained 
> > (except by chance) if that single vote is not transferable (as in the 
> > Single Non-Transferable Vote).
> 
> That's not completely true. Some methods that don't use transferable 
> votes have a strategy equilibrium where there's PR. Consider, for 
> instance, SNTV (you get one vote, the n best wins), under party control. 
>   If a given party fields too many candidates, their votes are spread 
> too thin and they lose. If the party fields too few candidates, they 
> miss some seats they could otherwise have acquired. Thus each party 
> fields a number of candidates proportional to that party's support, and 
> instructs the people to vote randomly for one of the party' candidates 
> (so as to spread the votes evenly).
> 
> You may argue that the random part of the allocation constitutes chance, 
> but it doesn't have to. When Taiwan was using the SNTV, one of the 
> parties instructed the voters to decide which candidate to vote for 
> according to the voter's birthday. That's uniform but it's not random 
> (since the birthday remains the same).
> 
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