[EM] Nightmare On IRV Street ?

Dgamble997 at aol.com Dgamble997 at aol.com
Fri Jul 4 15:35:02 PDT 2003

Firstly my example, yes Adam and Kevin your analysis is correct. A casting a 
second preference for B serves only to defeat C and elect B and vice versa.

The collective result however of these two strategies under Condorcet is that 
neither A  or C supporters get their first choice. If both A and C express a 
single preference each has a 50% chance of getting their first choice. As it 
is B wins with 14% support under Condorcet.

Adam Tarr wrote

Can you really put the Condorcet "nighmare" scenario I wrote in the same 
ballpark as the IRV nightmare scenario?  My Condorcet scenario ends with 
the compromise candidate winning, and nobody regretting their vote.  In the 
IRV scenario I showed, the clearly, indisputably pre-eminent candidate 
loses, and a third of the electorate is kicking themselves on election night.

No I don't put the Condorcet "nightmare" in the same ballpark as the IRV 
"nightmare" I feel it is worse. I am not at all happy- for all sorts of "turkey" 
reasons explored extensively in previous posts-  with  any single member system 
that can elect  candidates with a low first preference vote. I see your 
nightmare IRV scenario as an acceptable scenario which could occur in a close race 
where the electorate is divided into three approximately equal factions- no 
method is perfect and elections will sometimes be close.

Adam also wrote

That's a pretty big non sequitur there.  Why IRV?  Simply because that's 
what the largest US electoral reform group supports?

No not at all. I'm not prone to supporting things simply because certain 
groups or people say so. My argument in favour of IRV is as follows:

1/ IRV prevents a minority winning an election because the majority divides 
its support between 2 or more candidates.

2/ IRV ( compared to plurality) tends to elect moderate compromise candidates 
who enjoy general support.

But doesn't Condorcet do these things as well, in fact doesn't Condorcet do 
these things much better ?

The answer is of course yes. Condorcet does them better, Condorcet does them 
too well. In a 3 party ( right, centre, left) election with no absolute 
majority the centre candidate must come at least second to win under IRV. Under 
Condorcet s/he could win from third.

Considering this result in isolation from previous elections and the possible 
outcome of future ones Condorcet seems to be the better method.

Now to what could happen with Condorcet in practice. Condorcet favours 
centrist candidates and parties, in my opinion to too great a degree. Under 
Condorcet a centrist party would be very difficult to defeat. Swapping the 
Democrat/Republican duopoly for a centrist monopoly would not be good.  Effective one 
party states (like Mexico and India were for decades) are generally a bad thing. 
Periodic change in government is necessary for a healthy democracy. The 
Democrat/ Republican duopoly bears testimony to the dangers of excessive stability 
and stagnation.

IRV appears to strike a balance between ensuring that a candidate reflects 
the consensus and  enjoys general support and the alternation of government 
necessary for a healthy democracy.

David Gamble 

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