From: (Gerry Gryschuk)
Subject: Re: Proportional representation
Organization: University of Saskatchewan
Date: Fri, 6 Nov 1992 12:39:20 GMT

From article <1d9q47INN68t@iskut.ucs.ubc.ca>, by mathew@unixg.ubc.ca (Mathew B Englander):
> dat@thinkage.on.ca (David Adrien Tanguay) writes:
>>What are the cons of a transferable vote system? (i.e., where the voter ranks
>>all candidates, somewhat similar to the way the party leaders are chosen)
>>It would seem to preserve the ideological direction of the electorate, yet
>>limit the representation to the more popular parties, helping to avoid
>>parliamentary deadlock.
> 
> The greatest problem is that candidates can be hurt by an *increase* in
> support. For example, suppose that candidates A, B, and C are running 
> for the party leadership. Suppose that there are 675 voting delegates
> divide roughly into four groups:
> 
> 	Group I: 150 voters, whose ordered preference is A, B, C
> 	Group II: 100 voters,  "      "        "      "  A, C, B
> 	Group III: 200 voters, "      "        "      "  B, C, A
> 	Group IV: 225 voters,  "      "        "      "  C, A, B.
> 
> (What I mean here is that, for example, Group II prefers A to C, but
> prefers C to B -- and thus presumably prefers A to B.)
> 
> Now, what happens in the vote? On the first ballot, the results are
> 
> 	A: 250 (Groups I and II)
> 	B: 200 (Group III)
> 	C: 225 (Group IV).
> 
> No candidate has a majority, and since B has the lowest total he is
> eliminated and A and C have a "runoff". Note now that the 200 voters
> in Group III will now vote for their 2nd-favourite candidate, C.
> So the second ballot results are
> 
> 	A: 250 (Groups I and II)
> 	C: 425 (Groups III and IV).
> 
> And C wins the leadership.
> 
> So far, so good. But what would have happened if, before the first
> ballot, C did some last-minute campaigning and won over all the members
> of Group II (which gets renamed Group II*). The breakdown of groups now
> becomes:
> 
> 	Group I: 150 voters, whose ordered preference is A, B, C
> 	Group II*: 100 voters, "      "        "      "  C, A, B
> 	Group III: 200 voters, "      "        "      "  B, C, A
> 	Group IV: 225 voters,  "      "        "      "  C, A, B.
> 	
> Since C has increased her support, and she would have won even without
> this increase, we would expect her still to win now. But does she?
> The new first ballot results are:
> 
> 	A: 150 (Group I)
> 	B: 200 (Group III)
> 	C: 325 (Groups II* and IV).
> 
> So A is eliminated, and Group I supports its second choice, B, on the
> second ballot:
> 
> 	B: 350 (Groups I and III)
> 	C: 325 (Groups II* and IV).
> 
> So B wins! The shift of voters *toward* C actually caused C to lose
> the race. This is why this sort of voting is fundamentally flawed.
> 

Sorry I don't normally leave in the whole post just to respond a little at
the end but I think it's necessary here.

Anyway, yes this method would be flawed. However a simple fix would be to
set a fixed number of "points" to the place a person voted a candidate.
Simply base it on the number of candidates running and no problem should
arise. That is in your examples a first place vote is worth 3, second 2 and
3rd 1. In this case C wins both times and by a wider margin in the second
scenario as she should. The math is left as an excercise for the reader.

I believe this might be the way Australia does it, I could be wrong though.
I do know they use STV of some sort.
--
Gerald Gryschuk            Saskatoon,Saskatchewan = a place with 9 months
gerry@sask.usask.ca           of hockey and 3 months of poor skating.
Go Habs!!!		              (The Bum rules!!!)
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