[EM] No evidence that IRV doesn't fail. Reasons why it must

Eric Gorr eric at ericgorr.net
Fri Jan 23 16:22:03 PST 2004

At 6:56 PM -0500 1/23/04, Dgamble997 at aol.com wrote:
>Eric Gorr wrote:
>>Yes, I can invent numbers that show just the opposite.
>Yes, exactly my point.
>In the original examples only rankings, not rankings with utilities 
>were given. Without information on the actual utilities the 
>Condorcet winner might have the highest utility or might not. You 
>just don't know.

Then, how can you reject a Condorcet winner, based on utilities?

"So why do I think the Condorcet winner is correct in the first 
example and the IRV winner in the second? It is a question of the 
utility of the candidates."

Since, I agree, you cannot know anything about the utility of the 
candidates with IRV or Condorcet, no decision on the merits of either 
method can be made and any rejection of a winner (as you have clearly 
done), is simply invalid.

>You cannot say from rankings alone (as you did)

I agree. My statement was in error.

So, we agree, we are left with just the rankings...so, what can we 
say about the example:

   47 A>B>C
   4  B>A>C
   2  B>C>A
   47 C>B>A

We can clearly say that the two largest groups would rather have B 
rather then their primary opposition. As such, it seem clear that B 
should be the winner rather then a clearly extremist candidate, which 
IRV would select in this case because IRV does not consider the lower 
preferences to be as important as the highest preference.

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