[EMAIL PROTECTED]">Guilty. I had thought of this problem once before when thinking about IRV'sHere's an inconsistency of IRV that I wish somebody had told me about
before I submitted my article to the Green Voice.
It is possible for a candidate to "win" every precinct without winning the
election.
failure to meet the Summability Criterion, but it wasn't on my mind when
I reviewed your article. Every elimination in IRV means going back to the
original ballots and eliminating the loser of the round, then recounting (you
can sum the ballots into bins for each possible combination of votes such as
A, AB, ABC, ACB, AC, ACD, etc., but this array gets very large very
quickly as the number of candidates goes up, as we saw here a few weeks
ago). That means per-precinct vote totals are useless. You have to do the
elimination globally, not locally, and that means you can't predict the
results from local data. Even if all localities pick the same winner.
So IRV is a great randomizer, but not a very good tool for democracy.
Another consequence of the summability failure is that reporting IRV
results will be very complicated. At least for Condorcet you could
publish the overall pairwise matrix (and also the pairwise matrices for
individual counties or precincts or whatever the desired resolution is).
[EMAIL PROTECTED]">This is a myth that IRV proponents have concocted. They want to foolNote that (lone mark) plurality does not suffer from this inconsistency.
Why is IRV considered better than plurality when it fails this consistency
test and also fails monotonicity?
the public into believing that it's the best method, and for those who aren't
as easily fooled, they want to be able to claim "Even if Approval or
Condorcet is better, IRV is still an improvement over the system we have
now, and besides it is the method with the political momentum behind it."
Supporting IRV because it has momentum is a persuasive idea only if IRV
is in fact better than Lone-Mark Plurality, which it isn't.
The problems with IRV can be summarized as follows:
When IRV declares a winner, the only evidence supporting that winner is
that the winner is preferred by a majority to all other candidates remaining
in the last round. There is no evidence that the winner is preferred by a
majority to the candidates that were eliminated in early rounds. Consequently,
for every round prior to the decisive round, IRV is throwing away
information.
The other problems with IRV (including the local/global consistency
problem) are manifestations of the way it trashes information.
Richard
