Actually, "differs from plurality" is not a sure indication of failure
for ranked voting - either IRV or Condorcet.
For Plurality, voter can name only ONE candidate.
For ranking, voter can vote for more than one, perhaps ranking most
desired over more gettable.
Condorcet will use all that is in the ballot.
IRV will discard some, use the top of what is left, and never
see the bottom of what is left.
So, three different methods each seeing parts of the voter's ballot.
My guess is that the top of the IRV ballot is what the voter is
presumed to have chosen in Plurality.
Dave Ketchum
On Nov 13, 2010, at 5:43 PM, Kathy Dopp wrote:
Message: 1
Date: Sat, 13 Nov 2010 22:17:49 +0200
From: Juho <[email protected]>
To: Election Methods <[email protected]>
Subject: Re: [EM] breakdown of Oakland mayor ballots
Message-ID: <[email protected]>
Content-Type: text/plain; charset="us-ascii"; Format="flowed";
DelSp="yes"
- I decoded the ballot images few days ago since there was some
interest on the rangevoting list =>
http://groups.yahoo.com/group/RangeVoting/message/14474
- Warren Smith wrote down some notes on the results =>
http://groups.yahoo.com/group/RangeVoting/message/14483
Looks like IRV lucked out and dodged a bullet for a change when it
differed from plurality for the first time in San Francisco and got it
right. As Warren Smith points out, if a little over 3,100 more voters
had ranked Kaplan 1st and Quan 2nd, Perata dead last, then Perata
would have won instead. We won't have to wait long until IRV gets
it wrong when it differs from plurality voting, according to the odds
Warren calculates.
http://rangevoting.org/Oakland2010Mayor.html
explains. Juho's data processing appears to be correct.
Quan was the Condorcet and IRV winner.
Perata was the plain plruality winner.
PARADOX:
If 3135 extra Kaplan>Quan>...>Perata votes are
added, all ranking Perata dead last and Quan 2nd, that
causes Perata to (then) win.
It is fortunate for them that those Perata-hating voters stayed home!
--------
IRV is is hardly worth all the extra costs and complexity and lack of
auditability when the chance is so high of not getting a good outcome
like this whenever the result differs from plurality.
Kathy Dopp
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