[EM] Instant Runoff Voting 3-candidate elections - pathologies considerably more common than you may have thought

[Warren Smith]

http://rangevoting.org/IrvParadoxProbabilities.html

computes the probabilities of a lot of pathologies in IRV3.
It is, I believe, the best available such computation.

The "total paradox probability" in such elections, i.e. the
probability that at least one among the 8 pathologies {Q, R, U, V, W,
X, Y, Z} occur in a random election, is found to be
    24.59%,   13.98%,   and 27.50%
in our three different probability models. But if we restrict
attention to elections in which the IRV process matters, i.e. in which
the IRV and plain-plurality winners differ (i.e. exactly the elections
IRV-advocates tend to cite as examples of the "success" of the Instant
Runoff Voting process), the total paradox probability becomes
stunningly large:
     74.10%,   72.61%,   and 54.44%
For the most part, this was not previously recognized. This goes a
long way toward explaining why it has been so incredibly easy for
people like me to find pathologies in real-world IRV elections,
seemingly most of the time we ever looked at any interesting IRV
election for which we could obtain enough data, and seemingly
especially in the elections cited by IRV-advocates as "great
successes" for IRV.

It is reasonable, in the face of such massive and frequently-arising
evidence that IRV has (obvious) problems, to promote it, as opposed to
some simpler method largely free of such problems?

-- 
Warren D. Smith
http://RangeVoting.org  <-- add your endorsement (by clicking
"endorse" as 1st step)
and
math.temple.edu/~wds/homepage/works.html