[EM] breakdown of Oakland mayor ballots

[Dave Ketchum]

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 <juho4880 at yahoo.co.uk>
>> To: Election Methods <election-methods at electorama.com>
>> Subject: Re: [EM] breakdown of Oakland mayor ballots
>> Message-ID: <8C9F038F-E57B-4589-A102-41B7A91BF7FC at yahoo.co.uk>
>> 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