[EM] breakdown of Oakland mayor ballots

[Kathy Dopp]

On Sat, Nov 13, 2010 at 9:46 PM, Dave Ketchum <davek at clarityconnect.com> wrote:
> 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.

David,  Not sure why you are restating the obvious.    You also are
mischaracterizing what I said. Let me try again so you can hopefully
get my meaning:

I said that for the first time that IRV/STV in San Francisco found a
different winner from the winner who would have won using plurality
methods (only counting voters' first choices). In other words the
IRV/STV winner has been the voters' 1st choice winner until now, so
that the extra costs of using IRV/STV produced essentially nothing
until this election.

My statement has nothing to do with other means of counting rank
choice ballots such as Condorcet. SF does not use Condorcet.

>
> 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.

Not sure that anyone on this list doesn't already know that, so not
sure why you're restating the obvious Dave.

>
> So, three different methods each seeing parts of the voter's ballot.  My

You just mentioned two methods of counting rank choice votes, not three.

> guess is that the top of the IRV ballot is what the voter is presumed to
> have chosen in Plurality.
What I said is copied below in case you're wondering what I said.

Warren Smith has proven that IRV has a very high probability of
producing vagaries in cases when it does not produce the same results
as a plurality election would. Most often, as we've seen, IRV/STV
produce the same results as a plurality election in practice, as was
clear if you read the news articles on this SF election.

When IRV/STV does not replicate plurality results, it has a high
probability of producing results that are nonmonotonic or eliminate
the voters' favorite candidate (Condorcet winner).

I hope that clarifies for you. I apologize failing to include enough
information for you to understand what I said.  Perhaps you had not
read the two news articles on the election like I had, nor read Warren
Smith's prior article that shows how this latest election dodged a
bullet.

Again, there will not be very many cases like this when IRV fails to
elect the plurality winner and actually elects the Condorcet winner.
I suggest you read Warren's article on that issue.

Kathy


>>> - 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
>
>
>



-- 

Kathy Dopp
http://electionmathematics.org
Town of Colonie, NY 12304
"One of the best ways to keep any conversation civil is to support the
discussion with true facts."

Fundamentals of Verifiable Elections
http://kathydopp.com/wordpress/?p=174

Realities Mar Instant Runoff Voting
http://electionmathematics.org/ucvAnalysis/US/RCV-IRV/InstantRunoffVotingFlaws.pdf

View some of my research on my SSRN Author page:
http://ssrn.com/author=1451051