[EM] The responsiveness of Condorcet / Monotonicity

Dgamble997 at aol.com Dgamble997 at aol.com
Mon Jul 14 15:29:02 PDT 2003

Adam Tarr wrote:

"Doesn't that suggest that arguing that Condorcet is bad because it fails to 
produce proportionality, is sort of missing the point?"

No not exactly, Plurality and IRV in single seats can give a party 70 % of 
the seats for 35- 40%  of the vote. This is a bad thing.

Condorcet in single member seats has the potential to give a party that 
positions itself in the centre 70 % of seats with 20% of the vote. This is a worse 
thing ( even if the party is the most generally preferred party).

Adam also wrote:

"Right, candidates who appeal to the largest group of voters tend to win 
Condorcet elections.  You say this like it's a bad thing.  Such a candidate also 
always wins IRV elections if the voters use sufficiently intelligent strategy.  
Smart voters who realise their edge candidate will lose in the final runoff 
will abandon their first choice and vote for the centrist.  It's just easier 
and requires less guesswork on the voter's part with a good Condorcet method."

A lot of the argument in the well explored turkey thread involved how the 
word appeal could be replaced with the words " does not offend" or  " is disliked 
least ".


"The point was simply that, if you had to pick a party that was going to be 
disproportionately represented, you'd want it to be the most moderate party.  
IRV (and plurality for that matter) can produce disproportionate results that 
swing wildly from too far left to too far right."

Yes I suppose that's true. I'd really prefer that nobody was over (or under) 

"Has ANYONE on this list said that they want single-member districts using 
Condorcet voting?  I don't remember ever hearing that.  Some people have 
expressed a desire to have single-winner districts in the past (to get a closer link 
to the voters) but most offer a caveat of some mixed member proportionality."

Yes you are correct, I thought I had seen such posts but I can't find them 
now . I am glad to be proved wrong on this point. It is reassuring that nobody 
has proposed such a dubious idea.

Eric Gore wrote:

What about situations where PR is not appropriate?

Would it be accurate to say that you disagree with Arrow that a 
voting system should be monotonic? (IRV is not)
The only situations when PR is not appropriate is when PR is not possible. In 
those instances ( for a single position) we are left with trying to use the 
least bad single seat method.

Whilst leaving to one side what Arrow may or may not have said about 
monotonicity. I think the following:

Monotonicity is undoubtedly a desirable feature of an electoral method. I do 
however feel that no method can be perfect and that other features are more 
important ( proportional representation of parties, proportional representation 
of opinion, maximum freedom of  voter choice regarding the individuals who 
represent you, etc).

As to the non-monotonicity of IRV and STV let me give an alternative 
definition of non-monotonicity 

" Non-monotonicity -something that occurs more frequently in theoretical 
examples than real elections "

I am aware that certain people who post to electoral systems list have a " 
thing" about monotonicity ( or a lack of it) and that for certain people ( and I 
wasn't thinking of Eric) this can sometimes appear to reach the proportions 
of a morbid obsession.

David Gamble






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