[EM] IRV vs Condorcet

Dave Ketchum davek at clarityconnect.com
Thu Jul 24 00:50:01 PDT 2003

Seems to me Condorcet has pretty well won this one within EM, as I believe 
it deserves.

But, if I listen outside the door, IRV is making so much noise that few 
realize Condorcet exists, let alone that it is a preferable competitor.

Perhaps we need to sort out the similarities and differences more 
carefully, and get into more publicity.

SIMILARITY:  BOTH do ranked voting, with identical ballots, intending to 
identify the best liked candidate, and usually agreeing as to winner.  As 
we debate we concentrate on cases for which they differ, for those are the 
cases which are a source for debate.

DIFFERENCE:  While Condorcet compares EACH pair of candidates and develops 
a matrix of pair counts to identify best liked, IRV puts emphasis on 
patterns, giving preference to those that are ranked first.  See example 
below where B is much more popular than A, but IRV never sees this for C 
is more popular than B among B backers - even though all these C backers 
like B better than A.
      Some call this an argument for IRV, claiming that those C votes were 
against B.  Could be, sometimes, but more likely is a simple minor 
disagreement within B's party that does not create a smidgen of desire to 
have A win.

      Condorcet precinct results are a matrix small enough to publicize at 
that level, as well as being summable and publicizable at any level, 
including the whole district - even state level for governor.  Even 10 
candidates would be manageable for this - a 10x10 matrix.
      IRV must forward a count of how many voters vote each pattern, or 
take part in the counting by forwarding first the first rank counts, and 
then forwarding changes as each loser is eliminated.  Given 10 candidates 
there are a zillion possible patterns to forward - too many to publicize 
something understandable for many candidates at precinct level.
      IRV can also offer an ugly surprise - a handful of absentee ballots 
can change the order of attending to losers, resulting in changing winner 
when there was no visible reason for expecting this.  Absentee ballots 
could also change the Condorcet winner - but this is possible only when 
the candidates were close to a tie.
      Condorcet cycles can also disturb some.  Worth remembering that 
members of a cycle are near ties, identified as beating all outside the 
cycle.  Thus, while there MUST be a predefined rule for resolving a cycle, 
just as for resolving a true tie, this is not a reason for giving up on 

Example, designed to show difference between IRV and Condorcet:
      40 A
      30 C>B
      30 B
This is incomplete - one last ballot to count.  Last voter votes:
      A - odds are against this, and leaves us a tie problem.
      B - IRV and Condorcet agree that B wins:
           IRV - C becomes loser.
           Condorcet - B>A and B>C.
      C>B - disagreement:
           IRV - B loses; C loses; A wins; GREAT unhappiness among B backers.
           Condorcet - a cycle, B>A and A>C and C>B, but B>A is stronger 
than C>B, so B backers are pleased.

Other competition:
      Plurality - don't know why anyone reads this far if they are not 
ready to move on for something better.
      Reruns of any sort - ask the French if these are not risky, while 
being expensive.
      Approval - actually more complex for the voter than ranked voting - 
all that is needed for rank is better vs worse, Approval requires judgment 
as to cutoff, but does not let the voter express the ranking required to 
get this far.
      PR - debate this another day - for the moment I am staying with 
elections with single winners, and not concerned with legislatures where 
PR MIGHT make sense.
      Others - reject most for being complex, hard for voter to 
understand, and/or being subject to strategies.

Condorcet method details:
      Seems correct and agreed that voters can give identical rank when 
candidates seem to deserve it.  If it matters to the counting, give each 
candidate of a pair half a win (remember that Condorcet is doing only one 
pair at a time - 3 equal candidates will tie in 3 pairs).  IRV could be 
unwilling to touch this one.
      Seems right and agreed that voters not be required to rank all 
candidates - all not ranked are tied for last (except I would not count 
even half wins among these).
      Seems right to me that a voter should not be required to use every 
rank - rank 2 is better than rank 4, and it should not matter when looking 
at these two whether there is a 3.
      While IRV gets away from most of Plurality's spoiler problems, it 
has a few of its own.  Condorcet simply DOES NOT DO spoilers.

Condorcet's matrices do not seem to get the positive attention I believe 
they deserve.  Because they are distorted little, if at all, by thoughts 
of spoilers or voting strategy, counts for minor candidates warn:
      Winners how serious they need to take these as warnings.
      Minor candidates whether they need to change their approach.

IRV backers claim: "requiring a majority of votes to win" - seems like a 
worthless claim:
      If they forbid truncation (an ugly thought), they could get there - 
by sometimes including ballots in which the voter showed dislike of the 
winner by ranking that candidate as that voter's almost last choice.
      With truncation permitted, a majority of the ballots could have been 
exhausted before they declare a winner from the remaining minority of the 
total ballots.
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.

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