[EM] IRV in action

Dave Ketchum davek at clarityconnect.com
Mon Apr 7 19:16:02 PDT 2003

On Sun, 06 Apr 2003 19:20:34 +0200 Markus Schulze wrote:

> Dear James,
> you wrote (1 April 2003):
>>IRV does ensure that the winner has the support of half or more of
>>those who are voting at the point when the final decision is made.
> Usually, this property is called "Condorcet Loser Criterion."
> ******
> You wrote (4 April 2003):
>>I am very sympathetic to Condorcet, but there must be serious questions
>>about the public acceptability of some of the results it is likely produce.
> When the voters have understood Condorcet then they will also accept
> situations where the winner has only very few first preferences.
> Similarily, when IRV is being used then the voters will also accept
> situations where an extremist is elected because all moderate
> candidates have been eliminated at earlier stages.

Depends.  If most of the voters agree that any one of several moderates 
would have been preferable to this extremist, then they can blame IRV for 
failing to see this, feeling that they should not have been duped into 
using a system that elects an extremist just because there were several 
candidates that agreed on moderation but differed on details.

> ******
> You wrote (5 April 2003):
>>Once the major parties saw the effect of the Condorcet system, their
>>supporters would "bullet vote" only for the parties' candidates.
> I guess that for every reasonable method there are situations where
> "bullet voting" is a useful strategy. I guess that when IRV is being
> used and there are three potential winners, then each party will
> ask their supporters to bullet vote.

Given the candidate's positions being equidistant:
      IRV - I see not how bullet voting matters, for nothing else is seen 
until/unless your candidate loses.
      Condorcet - bullet voting avoids indicating a preference between the 
other candidates - either offering a tie vote via bullet, or indicating an 
actual preference, could affect the outcome.  Not likely the bullet vote 
promoters can tell which a particular voter will prefer once they have 
20/20 hindsight.  Note that first preference is the strongest statement a 
voter can make for a candidate.

Given two candidates being siblings, far from the third:
      IRV - voters for a sibling candidate almost certainly want to give 
the other sibling second preference, to decrease the chance of the third 
candidate getting elected.  I would expect these two candidates to promote 
this voting.  I do not see the third candidate caring, as I said above.
      Condorcet - I see no difference from IRV for the sibling candidates. 
    Third candidate has the problem described above for Condorcet.

> Markus Schulze

  davek at clarityconnect.com    http://www.clarityconnect.com/webpages3/davek
   Dave Ketchum    108 Halstead Ave, Owego, NY  13827-1708    607-687-5026
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