[EM] RCV in SF Mayoral election
robert bristow-johnson
rbj at audioimagination.com
Sun Jun 10 19:32:43 PDT 2018
Remember to strip of the city council race on the bottom (with 00021 as a Contest_ID).
--r b-j rbj at audioimagination.com
"Imagination is more important than knowledge."
-------- Original message --------
From: Brian Olson <bql at bolson.org>
Date: 6/10/2018 7:46 AM (GMT-08:00)
To: EM <election-methods at lists.electorama.com>
Subject: Re: [EM] RCV in SF Mayoral election
Ok, a few lines of Python poking the raw data shows I must have some bug in my Condorcet implementation. Digging into that...
On Sun, Jun 10, 2018 at 10:08 AM, Greg Dennis <greg.dennis at voterchoicema.org> wrote:
Brian, how is it possible that those differ? Since all the other candidates are eliminated in the final round, shouldn't that necessarily be the same as the pairwise contest between those two?
On Sun, Jun 10, 2018, 9:46 AM Brian Olson <bql at bolson.org> wrote:
I processed the latest data (2018-06-09) and posted the results of the SF Mayor election using a few algorithms:https://bolson.org/~bolson/2018/SF_Mayor_20180605.html
The Condorcet win is now 97436 to 91740 for Leno over Breed.The IRV final round is still just 94783 to 94393.
I'm using my software posted at https://github.com/brianolson/voteutil
commands (needs maven installed for compiling Java, and needs Python3):
curl -O http://www.sfelections.org/results/20180605/data/20180609/20180609_ballotimage.txtcurl -O http://www.sfelections.org/results/20180605/data/20180609/20180609_masterlookup.txt
(mkdir -p ~/psrc && cd ~/psrc && git clone https://github.com/brianolson/voteutil.git && cd ~/psrc/voteutil/java && mvn package)python3 ~/psrc/voteutil/python/rcvToNameEq.py -m 20180609_masterlookup.txt -b 20180609_ballotimage.txt -o 20180609_%s.nameqjava -jar ~/psrc/voteutil/java/target/voteutil-1.0.0.jar --rankings --full-html --explain -i 20180609_Mayor.nameq >/tmp/a.html
On Sat, Jun 9, 2018 at 9:33 PM, Greg Dennis <greg.dennis at voterchoicema.org> wrote:
I quickly looked at the vote data and saw that lots of ballots are categorized as "Exhausted by Over Votes" and "Under Votes," but there is no data indicating exactly how those ballots were marked, so we lack enough information to be sure of final results.
Actually, all the data you need is available from that page. The "Ballot Image" file will give you the full cast vote record of every individual ballot, and the "Master Lookup" is the legend that tells you what each number means. If you have trouble interpreting the numbers, just ping me!
On Sat, Jun 9, 2018 at 4:36 PM, VoteFair <electionmethods at votefair.org> wrote:
On 6/9/2018 6:25 AM, Greg Dennis wrote:
> San Francisco always make the cast vote record public:
> https://sfelections.sfgov.org/june-5-2018-election-results-detailed-reports
I quickly looked at the vote data and saw that lots of ballots are categorized as "Exhausted by Over Votes" and "Under Votes," but there is no data indicating exactly how those ballots were marked, so we lack enough information to be sure of final results.
Converting instant-runoff counts into pairwise counts might be (probably is?) possible, but I don't have time to do that analysis.
> The probability of IRV not elected the Condorcet winner appears to be
> exceedingly low in practice. We're up to about ~200 IRV elections
> conducted nationwide since 2004 and Burlington 2009 is the only
> case so far.
Yes, circular ambiguity -- in which there is no Condorcet winner -- is rare when the number of ballots exceeds a few hundred.
> On Sat, Jun 9, 2018 at 2:07 AM, robert bristow-johnson
> <rbj at audioimagination.com <mailto:rbj at audioimagination.com>> wrote:
> the limitation to only three levels of ranking is a problem. if
> someone ranked all three levels and none of the candidates ranked
> were either London Breed nor Mark Leno, that voter was effectively
> "disenfranchised" by being unable to weigh in on the final choice of
> choosing the mayor.
Based on a very quick guesstimate it looks like about 30 or so ballots had this issue. Right?
That's not a big number, but a fair counting method -- such as pairwise counting -- would not have to discard any ballots.
The bigger number is "under votes" and admittedly pairwise counting cannot compensate for a voter saying "here is the only acceptable choice" (or two choices in this case).
It's great that these results are getting analyzed by people who do not drink the FairVote kool-aid.
In haste,
Richard Fobes
"The VoteFair guy"
On 6/9/2018 6:25 AM, Greg Dennis wrote:
San Francisco always make the cast vote record public:
https://sfelections.sfgov.org/june-5-2018-election-results-detailed-reports
Based on the most recent analysis of these numbers that I saw, Leno was
indeed the Condorcet winner, and if Breed were to beat Leno in the final
round, she would then necessarily be the Condorcet winner. The
probability of IRV not elected the Condorcet winner appears to be
exceedingly low in practice. We're up to about ~200 IRV elections
conducted nationwide since 2004 and Burlington 2009 is the only case so far.
On Sat, Jun 9, 2018 at 2:07 AM, robert bristow-johnson
<rbj at audioimagination.com <mailto:rbj at audioimagination.com>> wrote:
Richard, a few points:
the limitation to only three levels of ranking is a problem. if
someone ranked all three levels and none of the candidates ranked
were either London Breed nor Mark Leno, that voter was effectively
"disenfranchised" by being unable to weigh in on the final choice of
choosing the mayor. however, i think the news media made it clear
that the race was really gonna be between Leno, Breed, and Kim, so
these fringe voters might have a chance to insincerely mark either
Leno or Breed as their 3rd choice and betray their *true* third
choice and, in doing so, have an effect in the final round.
ignoring the problem of only 3 ranking levels, it is not possible
that London Breed is the Condorcet Winner (a.k.a. "pairwise
champion"). it might be the case that Mark Leno or Jane Kim is the
Condorcet Winner and if the latter is the case, this is another real
indictment against STV or IRV as a method of tallying RCV. and your
reverse namesake, FairVote, is partially (or mostly) to blame.
i wonder if the City of SF has a file of all of the cast and scanned
ballots and the full ranking for each. if so, and if they release
it to the public, we can investigate if there is a Condorcet Winner
and if that CW is or is not Mark Leno. this would be interesting.
L8r,
r b-j
> On 6/8/2018 6:24 PM, Christopher Colosi wrote:
> > ... She stated “This is the system we are working with. That’s
> > a discussion we can have at a later time. For now, we’re stuck
with it.”
> > - insinuating it is not fair. I was quite bothered to have a Dem
in a
> > progressive city insinuate that first past the post is more
fair. ...
>
> This remark does not imply support for first past the post (FPTP,
a.k.a
> plurality counting).
>
> There are other ways to count the preference marks on "ranked-choice"
> ballots. In particular, pairwise counting could be used instead of
> instant-runoff counting, and that is fairer than FPTP.
>
> > 1. May not elect majority candidate
> > ...
> > Is this common? This is
> > probably an abnormally close race. Thoughts?
>
> I doubt the voters would regard this as a close race if they had been
> able to fully rank all the choices. The 3-choice limitation is
> simplistic, and complicates the counting.
>
> Pairwise counting does not result in any exhausted ballots. Unmarked
> choices are an indication that the choices are equally disliked. And
> multiple candidates being marked at the same preference level is
also no
> problem.
>
> In other words, the ballots contain enough information that they
can be
> counted in other ways, besides instant-runoff counting. Those
alternate
> counting methods could reveal a clearer outcome.
>
> In haste,
> Richard Fobes
>
>
> On 6/8/2018 6:24 PM, Christopher Colosi wrote:
>> Curious to hear people’s thoughts on some issues.
>>
>> 1. May not elect majority candidate
>> In SF, we restrict to 3 choices to simplify the process. As the vote
>> currently stands, 144 votes separate the top two candidates
(<0.1%) and
>> over 16,000 ballots have been exhausted (all 3 choices eliminated).
>> About 9% of voters have been removed from the pool. It is very
possible
>> that the result would have shifted if they had the opportunity to
rank a
>> 4th candidate, and therefore, it is possible that we won’t elect the
>> person who truly represents the majority. Is this common? This is
>> probably an abnormally close race. Thoughts?
>>
>> 2. What are your thoughts on London Breed’s response to being
asked if
>> RCV is fair? She stated “This is the system we are working with.
That’s
>> a discussion we can have at a later time. For now, we’re stuck
with it.”
>> - insinuating it is not fair. I was quite bothered to have a Dem in a
>> progressive city insinuate that first past the post is more fair. It
>> also felt divisive. If Leno wins, will her supporters feel that
>> democracy prevailed, or that the election was stolen? She also
presents
>> herself as a minority candidate and it is my understanding that RCV
>> gives minority candidates better chances and causes all
candidates to be
>> more likely to campaign to minority communities. Am I mistaken? Are
>> there any legitimate arguments that FPTP can be more fair? Thoughts?
>>
>> Regards,
>> —Chris
>>
>>
>>
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r b-j rbj at audioimagination.com
<mailto:rbj at audioimagination.com>
"Imagination is more important than knowledge."
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