On 5/27/2013 12:19 PM, David L Wetzell wrote:
...
The short-comings of IRV depend on the likely number of serious
candidates whose a priori odds of winning, before one assigns
voter-utilities, are strong. If real life important single-winner
political elections have economies of scale in running a serious
election then it's reasonable to expect only 1, 2 or 3 (maybe 4 once in
a blue moon) candidates to have a priori, no matter what election rule
gets used, serious chance to win, while the others are at best trying to
move the center on their key issues and at worse potential spoilers in a
fptp election.
Plurality voting and limited voting (and the Borda count if the voters
are undisciplined) are about the only methods that _cannot_ handle 3 or
(maybe) 4 popular choices along with any number of unpopular choices.
So it seems disengaged from reality to let C, the number of candidates,
go to infinity... and if a lot of candidates are not going to get
elected then to disregard voter info/preference over them is of much
less consequence.
Although the number of popular candidates is now small, that's because
we use plurality voting. When we use better voting methods, the number
of popular candidates will increase; of course not to infinity, but
frequently beyond the 3 or 4 popular choices that IRV can handle with
fairness.
Although it's a non-governmental example, take a look at the current
VoteFair American Idol poll. The number of popular music genres is
about 5, and there are about 7 singers who get more than a few
first-choice votes.
http://www.votefair.org/cgi-bin/votefairrank.cgi/votingid=idols
IRV would correctly identify the most popular music genre (based on
current results), but probably would not correctly identify the most
popular singer.
Why would voters trust a voting method that stops getting fair results
with so few popular candidates?
Yes, IRV is easy to explain, but that advantage becomes unimportant as
the number of popular candidates increases, which it will when better
voting methods are adopted.
Richard Fobes
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