[EM] Arrow's Theorem

[Dave Ketchum]

On May 6, 2011, at 3:05 AM, Kristofer Munsterhjelm wrote:

> robert bristow-johnson wrote:
>
>> likewise, when the IRV method chooses the same candidate as  
>> Condorcet would (which is what would happen if the Condorcet winner  
>> makes it into the IRV final round), we can say "Hey, IRV did pretty  
>> good!"  but if IRV fails to elect the Condorcet winner, it doesn't  
>> make IRV appear more legitimate to the electorate.
>> so, in both cases; Electoral College and IRV, i would ask "Why  
>> bother?"  if the measure of goodness of the election result is how  
>> congruent it is with the Popular vote or Condorcet, respectively,  
>> why not just use the Popular vote and Condorcet instead of  
>> something that tries to approximate either?

Seems like Robert meant "or" rather than "and".
>
>
> Well, Fairvote would like to make us believe that some cases, if the  
> Condorcet winner had won, we'd all be saying "but wait! He didn't  
> have enough core support! Boo!".

But, we chose ranking rather than Approval to let voters approve, but  
with unequal liking.  Bush haters could want to vote both Gore and  
Nader as better, but not as equally liked - with whoever they ranked  
second still seen as better than Bush.
>
>
> (Presumably we should also be saying, if the Plurality winner won,  
> "but wait! Lots of people second-ranked someone else! Boo!". One  
> might wonder how much "core support" is enough.)

But, if the Plurality winner won without a runoff, all three methods  
would agree as to winner.