[EM] Condorcet loser elimination PR
chrisbenham at bigpond.com
Mon Jul 28 10:23:12 PDT 2003
James Green-Armytage wrote:
"Below is an illustrative example where, I think you will agree, your
revised method produces an unfair or counterintuitive result.
The election is between 5 candidates, for 3 seats.
There are 300 voters.
I will use a Hare quota, to keep things simple. (Yes, I know your method
specifies a Droop quota, but it doesn't matter for these purposes.)
The Hare quota is 300 / 3 = 100 votes.
The preference rankings are as follows:
86: A, B, C, D, E
15: B, A, C, D, E
15: D, E, C, B, A
84: E, D, C, B, A
I think that we can agree that the appropriate outcome is ACE, correct?
This is the outcome that plain STV gives, and it is the outcome that
Unfortunately, your revised method seems to produce an outcome of ABC."
I seriously doubt your claim that using a Hare instead of a Droop quota "doesn't
matter for these purposes". I remember long ago getting it on good authority that
compared to the Droop quota, the Hare quota is correctly superceded rubbish. This
view has been recently confirmed by James Gilmour:
"When Hare and Droop are applied to transferable preferential voting (eg STV-PR),
the effect of the Hare quota to over-represent smaller groups can deny a larger
party its fair share of the seats to the extent that it gets fewer seats than a
smaller party with fewer votes."
In the case of your example, the Droop quota is 300/4 = 75. Since ACE each have
more than a Droop quota of first preference votes, then I and my proposed method
agree that ACE is the "appropiate outcome".
So I am afraid I don't understand your point.
Looking forward to your reply,
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