[EM] Re: Issues, Condorcet, and IRV (was: IRV vs. plurality)

[Dave Ketchum]

On Fri, 8 Aug 2003 11:08:30 -0400 Eric Gorr wrote:

> At 3:03 AM -0400 8/8/03, Dave Ketchum wrote:
> 
>>      Except for cases involving IRV spoilers, winners are IDENTICAL - 
>> repeat IDENTICAL!!!
>>  Condorcet backers emphasize the IRV spoilers because those are the 
>> major reason for choosing Condorcet over IRV (Condorcet claims simpler 
>> counting of votes as an additional advantage).
> 
> 
> What do you mean by IRV Spoilers?


Looked to me as the same thing as happens under Plurality:
      In 2000, Gore backers griped that Nader got in their way in Florida.
      Here, C backers got in the way of B getting an easy win in IRV.

> 
> Candidates who run solely for the purpose of splitting the vote?


No - could happen, but:
      There was general agreement that the Greens had ZERO desire to help 
Bush win in 2000, and they debate right now as to how to approach 2004 - 
get some visibility (desirable), but help Bush (INTOLERABLE!!!). 
Possibilities include campaigning in NY (where they expect Bush to lose 
even with this), and not campaigning in swing states (where a third party 
could help Bush win if they tried).
      I defined my example as what I see as a likely event - MOST of the 
electorate is agreed as to being anti-A, while their internal contest 
between B and C simply exists, rather than representing a desire to commit 
party suicide.

> 
> I think it has already been shown that the winners between IRV and 
> Condorcet are not identical in more then just these cases.


I concede below that it can be other than odd cases.  As to odd cases:
      Markus recently hit us with a demonstration that Condorcet can be 
tortured into odd results with paper voters - and doing that particular 
torture with real voters seems unbelievable:
      Prospect was that A was winning, three more ballots turned up with A 
in first rank, and these ballots caused D to win.
      Method was to start with a particular method of resolving cycles 
(nothing wrong with the method - just provides knowledge for constructing 
the torture), provide a 6-member major cycle containing two 3-member minor 
cycles, and define vote counts for two pairs connecting the minor cycles 
such that lower ranks in the three odd ballots will change which of these 
pairs is discarded first, and thus which minor cycle contains the winner.

     Turns out the three voters could have succeeded via bullet voting, 

BUT, for all they knew without the vote counts in front of them, could 

have happened that their lower rank votes were needed to let the A cycle 

contain the winner.
> 
> For example, in many cases, especially ones involving polarizing issues 
> (i.e. abortion, gun control, etc.) you can have two fairly equal, but 
> opposing positions with a third option that would win, if and only if 
> (iff) the two groups at the poles liked it better then the other end of 
> the pole - which is by no means guaranteed.
> 
OUCH - agreed that with IRV the weakest third is dead and, for the ones you 
mention, that is likely to he the neutral third, while Condorcet would see 
if a majority would really tolerate neutral in preference to letting their 
enemies win (assuming they were unable to win for their end).

-- 
davek at clarityconnect.com  http://www.clarityconnect.com/webpages3/davek
  Dave Ketchum   108 Halstead Ave, Owego, NY  13827-1708   607-687-5026
            Do to no one what you would not want done to you.
                  If you want peace, work for justice.