[EM] Nightmare On IRV Street ?
Dgamble997 at aol.com
Dgamble997 at aol.com
Wed Jul 2 17:20:02 PDT 2003
Adam Tarr wrote
So here we have a more realistic "turkey" scenario. A candidate with a
core support of only 12% manages to win an election. Compare that, if you
will, to the nightmare scenario of IRV:
Centrist has the most first place votes, the most second place votes, and
the most third place votes. Centrist is the only candidate who does not
appear fourth or fifth on any ballot. Centrist would win in a landslide
over any other candidate in a two-way race. Centrist is quite obviously
the popular choice by ANY reasonable measure.
In Condorcet, plurality, top two runoff, or really any reasonable method,
Centrist wins. But in IRV, Centrist is eliminated before the final runoff,
and Right wins in a squeaker.
To me, the IRV nightmare scenario is obviously far worse. In my nightmare
scenario for Condorcet, no voter has any real reason to regret their vote
after the election, while in the IRV vote a solid third of the electorate
have good reason to regret their strategy.
Consider the following plurality nightmare:
Florida November 2000
Bush wins the 25 electoral college votes of Florida and thus the presidency.
Or the top two runoff nightmare:
First round of the French presidential election 21.04.2002
Chirac (RPR, right) 19.9%
Le Pen (FN, extreme right) 16.9%
Jospin (PS, left) 16.2%
other left ( 6 candidates) 21.3%
other ( 7 candidates) 25.6%
Divisions between candidates on the left propel a candidate of the extreme
right into the second round ensuring Chirac's victory as the only acceptable
candidate. A 3% fall in Chirac's support could have lead to a Le Pen / Jospin
run-off leaving the main stream right without a second round candidate.
The Condorcet nightmare :
B a low utility compromise candidate wins.
All single seat methods are capable of producing bad results.
This is why I believe that single member methods should only be used for
single offices ( mayor, governor, president, etc) and that multi-member bodies
should be elected by proportional representation. There is nothing and can be
nothing that is proportional about the allocation of a single seat. My preferred
single member method is IRV.
Forest Simmons wrote
> David Gamble wrote:
> > Due to the nature of the Condorcet method- which considers lower
> > before the fate of higher preferences is decided- condorcet would appear
> to me
> > to be a turkey electoral system.
Question: When IRV "decides the fate" of a candidate while leaving other
candidates in the running, what does it do to that candidate?
Answer: It eliminates that candidate.
Question: In view of this process of elimination, why would you want to
decide the fate of an "higher candidate" before the fate of a "lower
My answer to this point is as follows:
My preferred multi-member method is the single transferable vote. It is
considered an important principle in STV that lower preferences should neither help
nor harm higher preferences. The reason for this is that if by casting a
lower preference you can defeat a higher preference you are given a powerful
incentive not to cast lower preferences.
The election was to close to call, before the votes were counted it was
uncertain whether A or C would obtain the most first preferences ( and also
irrelevant considering A and C supporters second preferences).
Under Condorcet by casting a second preference for compromise candidate B
both A and C voters have effectively defeated their first choice and elected B.
Yes, I am aware that B is the most generally preferred candidate and that by
voting for B C supporters have also defeated A.
If a A and C voters had not expressed a 2nd preference and voted
A would have won, or if two votes had been cast differently C would have won.
Forest also wrote
Question: Why do IRV supporters believe that IRV is superior to Coombs?
I'm not saying that Coombs is any better than IRV, but the IRV supporter
arguments seem to support Coombs over IRV?
Speaking entirely for myself and not "IRV supporters in general" I dislike
Coombs for the same reason I dislike Condorcet namely it can give victory to a
possibly low utility candidate who is the second choice of most people but the
first choice of very few.
First count vote A 49, B 3, C 48. Under the Coombs rule eliminate the candida
te with the highest number of last preferences candidate A. Final result B
52, C 48.
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