[EM] IRV vs RCV

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[EM] IRV vs RCV

Rob Lanphier
Hi folks,

This morning, I updated the FairVote page on Electowiki:
<https://electowiki.org/wiki/FairVote>

...which was an updated copy of the intro from the Wikipedia article
about FairVote.   They changed their name in 2004 (from Center for
Voting and Democracy), and it's about time we finally updated
Electowiki to reflect that.

However, one line got under my skin:
> "in 2004 changed its name to FairVote to reflect its support of such platforms as ranked choice voting (RCV),"

Well, there's a lot of good reasons for them to change their name, but
reflecting their support for "ranked choice voting" seemed revisionist
to me.  So I disappeared down a rabbit hole to make my edits to the
Electowiki version.

If you're interested in the details, I encourage you to read my longer
history on Electowiki, but here's the abbreviated timeline:
* 1992 - "Center for Proportional Representation" (CPR) is formed
* 1993 - CPR changes its name to "Center for Voting and Democracy" (CVD)
* 1993 - Report published, calling it "preference voting" (in a nod to
Australia)
* 1997 - first use of "Instant Runoff voting" that I could find
* 2000 - http://fairvote.org/irv URL goes live on CVD's website
* 2004 - CVD changes its name to "FairVote"
* 2006 - http://fairvote.org/rcv URL goes live on FairVote's website,
in cooperation with the Arizona League of Women Voters
* 2013 - FairVote starts referring to IRV primarily as "Ranked Choice Votting"

What happened between 2006 and 2013 is left as an exercise for the reader.

At any rate: is this a problem worth worrying about?  Should we just
do what all of the cool kids are doing, and start referring to it as
"Ranked Choice Voting"?  I mean, come on, Jennifer Lawrence and Krist
Novaselic are on board (ok, since Jennifer Lawrence was born in the
90s, I have no problem referring to her as a "kid", but Krist
Novoselic is older than I am, so should I be respecting my elders?)

Rob
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Re: [EM] IRV vs RCV

fdpk69p6uq
On Fri, Dec 13, 2019 at 11:39 PM Rob Lanphier wrote:
Should we just
do what all of the cool kids are doing, and start referring to it as
"Ranked Choice Voting"?

No, that misleads people into focusing only on the ranked ballot, while remaining ignorant of the way(s) the ballots are tallied.  While FairVote may have good marketing reasons for doing that, it's not beneficial from a theory/education perspective.   Extra-confusingly, FairVote uses the same term for both single-winner IRV and multi-winner STV, though they produce different kinds of representation (such as Australia's House vs Senate).

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Re: [EM] IRV vs RCV

robert bristow-johnson


> On December 13, 2019 11:53 PM [hidden email] wrote:
>
>
> On Fri, Dec 13, 2019 at 11:39 PM Rob Lanphier wrote:
> > Should we just
> >  do what all of the cool kids are doing, and start referring to it as
> >  "Ranked Choice Voting"?
>
> No, that misleads people into focusing only on the ranked ballot, while remaining ignorant of the way(s) the ballots are tallied. While FairVote may have good marketing reasons for doing that, it's not beneficial from a theory/education perspective. Extra-confusingly, FairVote uses the same term for both single-winner IRV and multi-winner STV, though they produce different kinds of representation (such as Australia's House vs Senate).

i am also unhappy and negatively impressed with FairVote for appropriating the term Ranked-Choice Voting to replace the previous label Instant-Runoff Voting which has accumulated some negative cache.  They have always introduced the ranked ballot as only tallyable using IRV rules and appropriating the more general term RCV even more so conveys that misrepresentation.  FairVote is making it harder for people to unlearn that false connection.

but things are hard to change with election law.  while i like Ranked Pairs (using margins) better, i can see value in BTR-STV as a means to get a Condorcet-compliant method adopted as law.  We can say to the followers of FairVote that it's IRV with rounds.  And we can say it fixes the problem of risk of not electing the Condorcet candidate (if there is one).  it's Condorcet-compliant IRV and i wouldn't mind if they called that "RCV".

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Re: [EM] IRV vs RCV

Rob Lanphier
On Fri, Dec 13, 2019 at 9:21 PM robert bristow-johnson
<[hidden email]> wrote:
> but things are hard to change with election law.  while i like Ranked Pairs (using margins) better, i can see value in BTR-STV as a means to get a Condorcet-compliant method adopted as law.  We can say to the followers of FairVote that it's IRV with rounds.  And we can say it fixes the problem of risk of not electing the Condorcet candidate (if there is one).  it's Condorcet-compliant IRV and i wouldn't mind if they called that "RCV".

Yeah, I totally agree with all of this.  I also like Ranked Pairs, but
I suspect that all of the methods that pick a candidate out of the
Smith set are indistinguishable in real-world conditions.  My hunch is
that an analysis of the public elections that had ranked ballots would
reveal that all of them had a single Condorcet winner, and therefore
there would be no difference between the results of Ranked Pairs,
Schulze, Tideman, Schulze, or even Copeland.  So BTR-STV seems like a
fine compromise, since IRV has failed to pick the Condorcet winner in
at least one recent public election.

Rob
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Re: [EM] IRV vs RCV

James Gilmour
In reply to this post by Rob Lanphier
Is RCV (Ranked Choice Voting) really the same as IRV (Instant Run-off Voting)?

IRV (with preferential voting) surely had its origin as a replacement for successive (or top-two) FPTP run-off votes to determine
the winner in single-winner elections.  This single-winner application of STV preferential voting is known in some parts of the
world as the Alternative Vote, but that name never caught on in the USA.

Does RCV include multi-winner elections, i.e. STV-PR = preferential voting in multi-member electoral districts?

James Gilmour
Edinburgh, Scotland


> -----Original Message-----
> From: Election-Methods [mailto:[hidden email]] On Behalf Of Rob Lanphier
> Sent: 14 December 2019 04:39
> To: Election Methods <[hidden email]>
> Subject: [EM] IRV vs RCV
>
> Hi folks,
>
> This morning, I updated the FairVote page on Electowiki:
> <https://electowiki.org/wiki/FairVote>
>
> ...which was an updated copy of the intro from the Wikipedia article
> about FairVote.   They changed their name in 2004 (from Center for
> Voting and Democracy), and it's about time we finally updated Electowiki to reflect that.
>
> However, one line got under my skin:
> > "in 2004 changed its name to FairVote to reflect its support of such platforms as ranked choice voting (RCV),"
>
> Well, there's a lot of good reasons for them to change their name, but reflecting their support for "ranked choice voting"
> seemed revisionist to me.  So I disappeared down a rabbit hole to make my edits to the Electowiki version.
>
> If you're interested in the details, I encourage you to read my longer history on Electowiki, but here's the abbreviated
> timeline:
> * 1992 - "Center for Proportional Representation" (CPR) is formed
> * 1993 - CPR changes its name to "Center for Voting and Democracy" (CVD)
> * 1993 - Report published, calling it "preference voting" (in a nod to
> Australia)
> * 1997 - first use of "Instant Runoff voting" that I could find
> * 2000 - http://fairvote.org/irv URL goes live on CVD's website
> * 2004 - CVD changes its name to "FairVote"
> * 2006 - http://fairvote.org/rcv URL goes live on FairVote's website, in cooperation with the Arizona League of Women
> Voters
> * 2013 - FairVote starts referring to IRV primarily as "Ranked Choice Votting"
>
> What happened between 2006 and 2013 is left as an exercise for the reader.
>
> At any rate: is this a problem worth worrying about?  Should we just do what all of the cool kids are doing, and start referring
> to it as "Ranked Choice Voting"?  I mean, come on, Jennifer Lawrence and Krist Novaselic are on board (ok, since Jennifer
> Lawrence was born in the 90s, I have no problem referring to her as a "kid", but Krist Novoselic is older than I am, so should I
> be respecting my elders?)
>
> Rob
> ----
> Election-Methods mailing list - see https://electorama.com/em for list info

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Re: [EM] IRV vs RCV

Kristofer Munsterhjelm-3
In reply to this post by Rob Lanphier
On 12/14/19 5:39 AM, Rob Lanphier wrote:

> If you're interested in the details, I encourage you to read my longer
> history on Electowiki, but here's the abbreviated timeline:
> * 1992 - "Center for Proportional Representation" (CPR) is formed
> * 1993 - CPR changes its name to "Center for Voting and Democracy" (CVD)
> * 1993 - Report published, calling it "preference voting" (in a nod to
> Australia)
> * 1997 - first use of "Instant Runoff voting" that I could find
> * 2000 - http://fairvote.org/irv URL goes live on CVD's website
> * 2004 - CVD changes its name to "FairVote"
> * 2006 - http://fairvote.org/rcv URL goes live on FairVote's website,
> in cooperation with the Arizona League of Women Voters
> * 2013 - FairVote starts referring to IRV primarily as "Ranked Choice Votting"
>
> What happened between 2006 and 2013 is left as an exercise for the reader.
I'm thinking something that happened in 2009 was influential :-)

> At any rate: is this a problem worth worrying about?  Should we just
> do what all of the cool kids are doing, and start referring to it as
> "Ranked Choice Voting"?  I mean, come on, Jennifer Lawrence and Krist
> Novaselic are on board (ok, since Jennifer Lawrence was born in the
> 90s, I have no problem referring to her as a "kid", but Krist
> Novoselic is older than I am, so should I be respecting my elders?)

 From a purely descriptive perspective, "ranked choice voting" is voting
which involves choices arranged in ranks, so pretty much every kind of
ranked ballot would count. I'd be inclined to suspect that FairVote
calls IRV RCV to try to cement a link between ranked voting (the ballot
format) and IRV (their method).

I don't see that there's a reason to do this. I'd suggest that RCV or
Ranked choice voting direct to some page about ranked balloting, and
then have a Wikipedia-style disambiguation line at top saying something
like "This is about the ranked ballot format, to see the method FairVote
calls Ranked Choice Voting, go to [Instant Runoff Voting]".

To try to be generous to the other side, I could say that some methods'
names aren't entirely descriptive (e.g. Ranked Pairs), and that "ranked
choice voting" (why not just "ranked voting"?) is an odd term for the
general concept of ranked balloting. Such arguments would strengthen the
case for letting FairVote use RCV as a brand name for IRV/STV. But on
the balance, I think doing so gives FairVote too much of a say in just
what method ranked balloting should use.
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Re: [EM] IRV vs RCV

robert bristow-johnson
In reply to this post by Rob Lanphier


> On December 14, 2019 2:44 AM Rob Lanphier <[hidden email]> wrote:
>
>  
> On Fri, Dec 13, 2019 at 9:21 PM robert bristow-johnson
> <[hidden email]> wrote:
> > but things are hard to change with election law.  while i like Ranked Pairs (using margins) better, i can see value in BTR-STV as a means to get a Condorcet-compliant method adopted as law.  We can say to the followers of FairVote that it's IRV with rounds.  And we can say it fixes the problem of risk of not electing the Condorcet candidate (if there is one).  it's Condorcet-compliant IRV and i wouldn't mind if they called that "RCV".
>
> Yeah, I totally agree with all of this.  I also like Ranked Pairs, but
> I suspect that all of the methods that pick a candidate out of the
> Smith set are indistinguishable in real-world conditions.  My hunch is
> that an analysis of the public elections that had ranked ballots would
> reveal that all of them had a single Condorcet winner,

except, of course, Burlington Vermont 2009.

> and therefore
> there would be no difference between the results of Ranked Pairs,
> Schulze, Tideman, Schulze, or even Copeland.

this is the difficult point i have tried to say here.  i think that Schulze is likely the most resistant to voting strategy, but it's too difficult to explain to legislators and the public.

BTR-STV is different.  Schulze, RP, MinMax (dunno about Copeland) all elect the same candidate in the case of an CW or a Smith set of 3.  i don't ever ever ever expect to see a Condorcet RCV ever have a Smith set larger than and i really don't expect to see one without a CW.

>  So BTR-STV seems like a
> fine compromise, since IRV has failed to pick the Condorcet winner in
> at least one recent public election.

yes, and i am trying to remind the Progs of that.  but they are not listening.

--
 
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Re: [EM] IRV vs RCV

Bob Richard-2
In reply to this post by James Gilmour
James,

In the United States, the name RCV was adopted because some activists
wanted an umbrella term that would refer to both IRV and STV together --
and also not sound too technical. There are both pros and cons to this
as a political strategy. One of the several motivations was the belief
that voters and politicians could become accustomed to IRV --
politically a much easier reform to win -- and then persuaded to adopt
STV for the legislative branch later on.

--Bob Richard

------ Original Message ------
From: "James Gilmour" <[hidden email]>
To: "'Rob Lanphier'" <[hidden email]>; "'Election Methods'"
<[hidden email]>
Sent: 12/14/2019 6:26:13 AM
Subject: Re: [EM] IRV vs RCV

>Is RCV (Ranked Choice Voting) really the same as IRV (Instant Run-off Voting)?
>
>IRV (with preferential voting) surely had its origin as a replacement for successive (or top-two) FPTP run-off votes to determine
>the winner in single-winner elections.  This single-winner application of STV preferential voting is known in some parts of the
>world as the Alternative Vote, but that name never caught on in the USA.
>
>Does RCV include multi-winner elections, i.e. STV-PR = preferential voting in multi-member electoral districts?
>
>James Gilmour
>Edinburgh, Scotland
>
>
>>  -----Original Message-----
>>  From: Election-Methods [mailto:[hidden email]] On Behalf Of Rob Lanphier
>>  Sent: 14 December 2019 04:39
>>  To: Election Methods <[hidden email]>
>>  Subject: [EM] IRV vs RCV
>>
>>  Hi folks,
>>
>>  This morning, I updated the FairVote page on Electowiki:
>>  <https://electowiki.org/wiki/FairVote>
>>
>>  ...which was an updated copy of the intro from the Wikipedia article
>>  about FairVote.   They changed their name in 2004 (from Center for
>>  Voting and Democracy), and it's about time we finally updated Electowiki to reflect that.
>>
>>  However, one line got under my skin:
>>  > "in 2004 changed its name to FairVote to reflect its support of such platforms as ranked choice voting (RCV),"
>>
>>  Well, there's a lot of good reasons for them to change their name, but reflecting their support for "ranked choice voting"
>>  seemed revisionist to me.  So I disappeared down a rabbit hole to make my edits to the Electowiki version.
>>
>>  If you're interested in the details, I encourage you to read my longer history on Electowiki, but here's the abbreviated
>>  timeline:
>>  * 1992 - "Center for Proportional Representation" (CPR) is formed
>>  * 1993 - CPR changes its name to "Center for Voting and Democracy" (CVD)
>>  * 1993 - Report published, calling it "preference voting" (in a nod to
>>  Australia)
>>  * 1997 - first use of "Instant Runoff voting" that I could find
>>  * 2000 - http://fairvote.org/irv URL goes live on CVD's website
>>  * 2004 - CVD changes its name to "FairVote"
>>  * 2006 - http://fairvote.org/rcv URL goes live on FairVote's website, in cooperation with the Arizona League of Women
>>  Voters
>>  * 2013 - FairVote starts referring to IRV primarily as "Ranked Choice Votting"
>>
>>  What happened between 2006 and 2013 is left as an exercise for the reader.
>>
>>  At any rate: is this a problem worth worrying about?  Should we just do what all of the cool kids are doing, and start referring
>>  to it as "Ranked Choice Voting"?  I mean, come on, Jennifer Lawrence and Krist Novaselic are on board (ok, since Jennifer
>>  Lawrence was born in the 90s, I have no problem referring to her as a "kid", but Krist Novoselic is older than I am, so should I
>>  be respecting my elders?)
>>
>>  Rob
>>  ----
>>  Election-Methods mailing list - see https://electorama.com/em for list info
>
>----
>Election-Methods mailing list - see https://electorama.com/em for list info
>

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Re: [EM] IRV vs RCV

VoteFair-2
In reply to this post by Rob Lanphier
I just edited the Wikipedia page named "Ranked voting" to clarify that
it refers to using ranked ballots.  That's an edit that was already
discussed on the "talk" page for that article.  Previously the article
almost looked like a promo for Ranked Choice voting.

I don't like FairVote using the name "Ranked Choice voting," yet
fighting that name seems wasteful.

Instead I tell people we needed "ranked ballots and pairwise counting."
That separation of ballot type from counting method seems to help people
understand that ranked ballots can be counted in more than one way --
which is a point that's now stated in the "Ranked voting" Wikipedia article.

The article still needs further work, such as filling in the Condorcet
section, so anyone is welcome to improve it.  (I'm juggling multiple
projects so I just fixed the biggest problem.)

Richard Fobes

On 12/13/2019 8:39 PM, Rob Lanphier wrote:

> Hi folks,
>
> This morning, I updated the FairVote page on Electowiki:
> <https://electowiki.org/wiki/FairVote>
>
> ...which was an updated copy of the intro from the Wikipedia article
> about FairVote.   They changed their name in 2004 (from Center for
> Voting and Democracy), and it's about time we finally updated
> Electowiki to reflect that.
>
> However, one line got under my skin:
>> "in 2004 changed its name to FairVote to reflect its support of such platforms as ranked choice voting (RCV),"
>
> Well, there's a lot of good reasons for them to change their name, but
> reflecting their support for "ranked choice voting" seemed revisionist
> to me.  So I disappeared down a rabbit hole to make my edits to the
> Electowiki version.
>
> If you're interested in the details, I encourage you to read my longer
> history on Electowiki, but here's the abbreviated timeline:
> * 1992 - "Center for Proportional Representation" (CPR) is formed
> * 1993 - CPR changes its name to "Center for Voting and Democracy" (CVD)
> * 1993 - Report published, calling it "preference voting" (in a nod to
> Australia)
> * 1997 - first use of "Instant Runoff voting" that I could find
> * 2000 - http://fairvote.org/irv URL goes live on CVD's website
> * 2004 - CVD changes its name to "FairVote"
> * 2006 - http://fairvote.org/rcv URL goes live on FairVote's website,
> in cooperation with the Arizona League of Women Voters
> * 2013 - FairVote starts referring to IRV primarily as "Ranked Choice Votting"
>
> What happened between 2006 and 2013 is left as an exercise for the reader.
>
> At any rate: is this a problem worth worrying about?  Should we just
> do what all of the cool kids are doing, and start referring to it as
> "Ranked Choice Voting"?  I mean, come on, Jennifer Lawrence and Krist
> Novaselic are on board (ok, since Jennifer Lawrence was born in the
> 90s, I have no problem referring to her as a "kid", but Krist
> Novoselic is older than I am, so should I be respecting my elders?)
>
> Rob
> ----
> Election-Methods mailing list - see https://electorama.com/em for list info
>
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Re: [EM] IRV vs RCV

Rob Lanphier
In reply to this post by robert bristow-johnson
On Sat, Dec 14, 2019 at 7:21 AM robert bristow-johnson
<[hidden email]> wrote:
> > On December 14, 2019 2:44 AM Rob Lanphier <[hidden email]> wrote:
> > I also like Ranked Pairs, but
> > I suspect that all of the methods that pick a candidate out of the
> > Smith set are indistinguishable in real-world conditions.  My hunch is
> > that an analysis of the public elections that had ranked ballots would
> > reveal that all of them had a single Condorcet winner,
>
> except, of course, Burlington Vermont 2009.

I'm pretty sure all of the Condorcet-winner compliant methods chose
Andy Montroll, given the ballots from the Burlington 2009 election.
Copeland, Schulze, Ranked Pairs,  etc.  Was there a discrepency
between Condorcet methods, or just the well-documented discrepency
between the Condorcet methods and IRV?

> > and therefore
> > there would be no difference between the results of Ranked Pairs,
> > Schulze, Tideman, Schulze, or even Copeland.
>
> this is the difficult point i have tried to say here.  i think that Schulze is likely the most resistant to voting strategy, but it's too difficult to explain to legislators and the public.

Yeah, I agree.  I'm willing to take it on faith that BTR-STV is more
susceptible to strategy than methods that guarantee Smith set
membership, but I suspect that Condorcet-compliant methods perform
better at strategy resistance than standard IRV does.


> BTR-STV is different.  Schulze, RP, MinMax (dunno about Copeland) all elect the same candidate in the case of an CW or a Smith set of 3.  i don't ever ever ever expect to see a Condorcet RCV ever have a Smith set larger than and i really don't expect to see one without a CW.

Copeland isn't guaranteed to pick a candidate out of the Smith set
when the Smith set is bigger than one, so it's possible it'll pick a
different winner than Schulze, RP, MinMax, etc when the Smith set is
3.

> >  So BTR-STV seems like a
> > fine compromise, since IRV has failed to pick the Condorcet winner in
> > at least one recent public election.
>
> yes, and i am trying to remind the Progs of that.  but they are not listening.

*sigh*.  Yeah, sounds tough.  We had a close mayoral election here in
San Francisco in 2018.  Given how close it was, I was really terrified
that we'd end up with an election like Burlington 2009.  Thankfully,
the IRV elimination order didn't threaten to eliminate the Condorcet
winner.  The closeness of the race was between two candidates who
probably would have been the final two candidates in a BTR-IRV tally
(though the third place candidate wasn't far behind either of the
frontrunners).  Given the closeness bitterness of the race, it would
have been an electoral reform disaster if any of the top three
candidates had lost the way that Andy Montroll did in Burlington (as
the Condorcet winner and IRV loser).

Rob
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Re: [EM] IRV vs RCV

robert bristow-johnson


> On December 17, 2019 2:12 AM Rob Lanphier <[hidden email]> wrote:
>
>  
> On Sat, Dec 14, 2019 at 7:21 AM robert bristow-johnson
> <[hidden email]> wrote:
> > > On December 14, 2019 2:44 AM Rob Lanphier <[hidden email]> wrote:
> > > I also like Ranked Pairs, but
> > > I suspect that all of the methods that pick a candidate out of the
> > > Smith set are indistinguishable in real-world conditions.  My hunch is
> > > that an analysis of the public elections that had ranked ballots would
> > > reveal that all of them had a single Condorcet winner,
> >
> > except, of course, Burlington Vermont 2009.
>
> I'm pretty sure all of the Condorcet-winner compliant methods chose
> Andy Montroll, given the ballots from the Burlington 2009 election.
> Copeland, Schulze, Ranked Pairs,  etc.  Was there a discrepency
> between Condorcet methods, or just the well-documented discrepency
> between the Condorcet methods and IRV?

i misunderstood you.  we're on the same page.  yes, Burlington 2009 had a single, clear Condorcet winner.

it was the only IRV election that i know of where the Condorcet winner was not elected.


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[EM] Auditing IRV: RAIRE and SHANGRLA

Neal McBurnett
In reply to this post by Rob Lanphier
I just joined the list (after a few decades of activity with election methods and auditing). Thanks for the fascinating discussion.  This stuff is even more complicated than I knew.

Let me note one more complication though.  The interpretations by the voting system of the votes ("cast vote records" or CVRs) might
be wrong, and IRV is famously vulnerable to interpretation errors at each round of tallying.
Even figuring out how sensitive the outcome of a particular contest is to discrepancies between
the paper ballots and the CVRs is a challenging computation.

Thankfully, I can also pass on some news of progress in the field: the new RAIRE / SHANGRLA method of auditing IRV elections, which was piloted in the November 2019 election in San Francisco.  Armed with these techniques (and associated open-source code) we should be able to figure out how much error we could tolerate before an IRV tally might end up with a non-Condorcet winner, even though the tally of the official CVRs did pick a Condorcet winner.

And thus there's also more work to be done for any given election method to figure out how to audit it and limit the risk that the outcome is actually incorrect.

Background:

When we declare that a particular election resulted in a particular outcome according
to a particular algorithm, we are of course trusting that the election system interpreted the human input
with perfect accuracy and fidelity.  But of course we all know that computers make mistakes and are
vulnerable to hacking.

Ron Rivest and John Wack invented the concept of Software Independence to deal with that concern.

 Software Independence (Wack and Rivest)
  http://people.csail.mit.edu/rivest/RivestWack-OnTheNotionOfSoftwareIndependenceInVotingSystems.pdf

The field of Evidence-Based Elections presents a general framework for how to gather evidence to check
the outcome (set of winners) of a particular contest via software-independent evidence.

 Evidence-Based Elections  -  P.B. Stark and D.A. Wagner
  IEEE Security and Privacy, Special Issue on Electronic Voting, 2012.
  http://statistics.berkeley.edu/~stark/Preprints/evidenceVote12.pdf

Evidence-Based Elections employ Risk-Limiting Audits (RLAs) to sample some ballots, compare the paper with the electronic records, and limit the risk of declaring the wrong outcome.  In Colorado, we've pioneered and pushed forward the state of the art in RLAs as I describe here:

 https://bcn.boulder.co.us/~neal/elections/corla/

But defining RLAs for IRV has been a challenge for many years. Now a better method is available:

 RAIRE: Risk-Limiting Audits for IRV Elections - Michelle Blom · Peter J. Stuckey · Vanessa J. Teague
  https://arxiv.org/pdf/1903.08804.pdf

It can be used with the new more general RLA approach described in SHANGRLA:

 SHANGRLA: Sets of Half-Average Nulls Generate Risk-Limiting Audits: tools for assertion-based risk-limiting election audits
  https://github.com/pbstark/SHANGRLA

Which brings me to the post that prompted this post:

On Mon, Dec 16, 2019 at 11:12:24PM -0800, Rob Lanphier wrote:

> On Sat, Dec 14, 2019 at 7:21 AM robert bristow-johnson
> <[hidden email]> wrote:
> > >  So BTR-STV seems like a
> > > fine compromise, since IRV has failed to pick the Condorcet winner in
> > > at least one recent public election.
> >
> > yes, and i am trying to remind the Progs of that.  but they are not listening.
>
> *sigh*.  Yeah, sounds tough.  We had a close mayoral election here in
> San Francisco in 2018.  Given how close it was, I was really terrified
> that we'd end up with an election like Burlington 2009.  Thankfully,
> the IRV elimination order didn't threaten to eliminate the Condorcet
> winner.  The closeness of the race was between two candidates who
> probably would have been the final two candidates in a BTR-IRV tally
> (though the third place candidate wasn't far behind either of the
> frontrunners).  Given the closeness bitterness of the race, it would
> have been an electoral reform disaster if any of the top three
> candidates had lost the way that Andy Montroll did in Burlington (as
> the Condorcet winner and IRV loser).
>
> Rob

Re the 2018 San Francisco mayoral election that Rob alludes to, we can of course use RAIRE / SHANGRLA to audit the winner.
But he's also interested in whether the winner was a Condorcet winner. Related auditing techniques should be
able to calculate the minimum number of vote discrepancies that would have resulted in a different Condorcet winner.
But I don't know of anyone looking at that problem right now.

In general, if we want similar confidence in outcomes for other tally methods, we'll need to come up with RLA methods for them.
For many of the ranked-choice methods, RAIRE is probably a good model, and it might even provide insights in to other
aspects of voting methods.

Cheers,

Neal McBurnett                 http://neal.mcburnett.org/
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Re: [EM] Auditing IRV: RAIRE and SHANGRLA

robert bristow-johnson
Hello Neal,

Several things to say here:

1. Welcome to the EM list.  I am not any of the founding members, I was told about it 10 years ago by Terry Bouricius who is a fellow resident of Burlington Vermont, a past city councilor, a political scientist who works for FairVote, and an advocate for IRV, and as I found out a week ago when RCV began to reappear in Burlington, not much of an advocate for fixing what went wrong in Burlington in 2009.  I joined soon after the infamous Burlington 2009 IRV election, I believe the only one in which the Pairwise Champion (a.k.a. Condorcet candidate) did not win.  Much controversy and IRV was repealed the following year.

2. Although there is a relationship, the issues of Voting Methods (ballot type, FPTP, IRV, Condorcet, Score, Approval...) and Voting Security are not the same.  The only immediate connection between the two issues is that of precinct summability.  FPTP and Condorcet methods are both precinct summable, IRV is not unless you want to count all of the possible ways a ranked ballot can be marked and that is a very large number.

3. I took a look at the papers you reference and the only real Electrical Engineering aspect of this (one of the papers is IEEE) in my opinion (as an electrical engineer) is that of secure communications.  All that is important, but the auditing thing is just that, recounting ballots.  We do this routinely when the election is close or there is some other funny business.  To that, the only engineering solution, in my opinion are optical scan paper ballots, where the candidate name is on the physical instrument storing the vote (not those punch card butterfly ballots) so that the voter and the auditor see exactly the same ballot and there is no way a voter can think he/she voted for A but the physical instrument appears that he/she voted for someone else.  (If those punch cards were misaligned, you might end up voting for whom you hate the most.)  Regarding secure communications, having total transparency regarding all procedures, including the code use to scan and tabulate ballots, is the key.  It should be public domain and accessible by anyone.

I was talking with Jim Condos, the Vermont Secretary of State, about this and he said that there is a technology that will digitally photograph each ballot so that if it looks poorly marked, the system can flag a team of election officials, who can immediately pull up the ballot image and look and judge for themselves what the voter intent was.

One thing is, that if the election is in the U.S., the ballot must not, in any manner, be traceable to the identity of the voter who marked it.  If the ballots have serial numbers, those must not be associated with the voter.  That is different from the U.K. and some other democracies.

4. That said, I don't see what the big deal is.  If you have paper ballots *and* a manual recount is done, there is a way to do IRV manually with piles of ballots.  But it's laborious.  The issue of election security really is unrelated to the issue of whether the Condorcet candidate is elected or not.  Whether a particular IRV election will or will not elect the Condorcet winner is independent of security, redundancy, and auditing issues.  It's only a voting method issue.

5. I am skeptical of the "computers make mistakes" notion. Do you mean a hardware crash?  Because a numerical error with integer arithmetic is not really possible.

bestest,

r b-j

> On December 17, 2019 11:07 AM Neal McBurnett <[hidden email]> wrote:
>
>  
> I just joined the list (after a few decades of activity with election methods and auditing). Thanks for the fascinating discussion.  This stuff is even more complicated than I knew.
>
> Let me note one more complication though.  The interpretations by the voting system of the votes ("cast vote records" or CVRs) might
> be wrong, and IRV is famously vulnerable to interpretation errors at each round of tallying.
> Even figuring out how sensitive the outcome of a particular contest is to discrepancies between
> the paper ballots and the CVRs is a challenging computation.
>
> Thankfully, I can also pass on some news of progress in the field: the new RAIRE / SHANGRLA method of auditing IRV elections, which was piloted in the November 2019 election in San Francisco.  Armed with these techniques (and associated open-source code) we should be able to figure out how much error we could tolerate before an IRV tally might end up with a non-Condorcet winner, even though the tally of the official CVRs did pick a Condorcet winner.
>
> And thus there's also more work to be done for any given election method to figure out how to audit it and limit the risk that the outcome is actually incorrect.
>
> Background:
>
> When we declare that a particular election resulted in a particular outcome according
> to a particular algorithm, we are of course trusting that the election system interpreted the human input
> with perfect accuracy and fidelity.  But of course we all know that computers make mistakes and are
> vulnerable to hacking.
>
> Ron Rivest and John Wack invented the concept of Software Independence to deal with that concern.
>
>  Software Independence (Wack and Rivest)
>   http://people.csail.mit.edu/rivest/RivestWack-OnTheNotionOfSoftwareIndependenceInVotingSystems.pdf
>
> The field of Evidence-Based Elections presents a general framework for how to gather evidence to check
> the outcome (set of winners) of a particular contest via software-independent evidence.
>
>  Evidence-Based Elections  -  P.B. Stark and D.A. Wagner
>   IEEE Security and Privacy, Special Issue on Electronic Voting, 2012.
>   http://statistics.berkeley.edu/~stark/Preprints/evidenceVote12.pdf
>
> Evidence-Based Elections employ Risk-Limiting Audits (RLAs) to sample some ballots, compare the paper with the electronic records, and limit the risk of declaring the wrong outcome.  In Colorado, we've pioneered and pushed forward the state of the art in RLAs as I describe here:
>
>  https://bcn.boulder.co.us/~neal/elections/corla/
>
> But defining RLAs for IRV has been a challenge for many years. Now a better method is available:
>
>  RAIRE: Risk-Limiting Audits for IRV Elections - Michelle Blom · Peter J. Stuckey · Vanessa J. Teague
>   https://arxiv.org/pdf/1903.08804.pdf
>
> It can be used with the new more general RLA approach described in SHANGRLA:
>
>  SHANGRLA: Sets of Half-Average Nulls Generate Risk-Limiting Audits: tools for assertion-based risk-limiting election audits
>   https://github.com/pbstark/SHANGRLA
>
> Which brings me to the post that prompted this post:
>
> On Mon, Dec 16, 2019 at 11:12:24PM -0800, Rob Lanphier wrote:
> > On Sat, Dec 14, 2019 at 7:21 AM robert bristow-johnson
> > <[hidden email]> wrote:
> > > >  So BTR-STV seems like a
> > > > fine compromise, since IRV has failed to pick the Condorcet winner in
> > > > at least one recent public election.
> > >
> > > yes, and i am trying to remind the Progs of that.  but they are not listening.
> >
> > *sigh*.  Yeah, sounds tough.  We had a close mayoral election here in
> > San Francisco in 2018.  Given how close it was, I was really terrified
> > that we'd end up with an election like Burlington 2009.  Thankfully,
> > the IRV elimination order didn't threaten to eliminate the Condorcet
> > winner.  The closeness of the race was between two candidates who
> > probably would have been the final two candidates in a BTR-IRV tally
> > (though the third place candidate wasn't far behind either of the
> > frontrunners).  Given the closeness bitterness of the race, it would
> > have been an electoral reform disaster if any of the top three
> > candidates had lost the way that Andy Montroll did in Burlington (as
> > the Condorcet winner and IRV loser).
> >
> > Rob
>
> Re the 2018 San Francisco mayoral election that Rob alludes to, we can of course use RAIRE / SHANGRLA to audit the winner.
> But he's also interested in whether the winner was a Condorcet winner. Related auditing techniques should be
> able to calculate the minimum number of vote discrepancies that would have resulted in a different Condorcet winner.
> But I don't know of anyone looking at that problem right now.
>
> In general, if we want similar confidence in outcomes for other tally methods, we'll need to come up with RLA methods for them.
> For many of the ranked-choice methods, RAIRE is probably a good model, and it might even provide insights in to other
> aspects of voting methods.
>
> Cheers,
>
> Neal McBurnett                 http://neal.mcburnett.org/

--
 
r b-j                  [hidden email]
 
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Re: [EM] IRV vs RCV

Rob Lanphier
In reply to this post by robert bristow-johnson
On Tue, Dec 17, 2019 at 9:19 AM [EST] robert bristow-johnson
<[hidden email]> wrote:
> [At December 16, 2019 at 11:12 PM PST] Rob Lanphier <[hidden email]> wrote:
> > I'm pretty sure all of the Condorcet-winner compliant methods chose
> > Andy Montroll, given the ballots from the Burlington 2009 election.
> > Copeland, Schulze, Ranked Pairs,  etc.  Was there a discrepency
> > between Condorcet methods, or just the well-documented discrepency
> > between the Condorcet methods and IRV?
>
> i misunderstood you.  we're on the same page.  yes, Burlington 2009 had a single, clear Condorcet winner.

Cool.  I kinda figured it was a thinko, but I wanted to be
doubly-triply sure I check because I talk about Burlington 2009 so
much.

> it was the only IRV election that i know of where the Condorcet winner was not elected.

It's the only municipal IRV election that I've independently confirmed
the discrepancy as well.  But I haven't independently audited that
many municipal IRV elections.

I haven't analyzed /u/curiouslefty's claim that there was an
IRV/Condorcet discrepancy in Queensland Australia in 1998:
<https://www.reddit.com/r/EndFPTP/comments/e4ogcg/condorcet_failure_and_condorcet_cycle_analysis_of/>

In general, though, my hunch is that others can be found.  If
IRV/Condorcet discrepancies are truly one-in-a-million events under
real-world conditions, then we should stop obsessing about Burlington
2009, and get on board with
IRV/RCV/whatever-the-cool-kids-call-it-these-days.  But if the number
is more like one-in-a-hundred or maybe three-in-a-hundred with a naive
electorate (i.e an electorate that probably hasn't learned how to vote
strategically), then that's an enormous problem.  My hunch is that
it's closer to the latter, and that others can be found without too
much work because it's not that rare.

I'm aware of another ranked ballot election where there was an
IRV/Condorcet discrepancy: the 2003 Debian leader election.  Debian
uses Condorcet-Schulze, so the pairwise winner won the election.  But
intuitively, the result seemed to fall in the jagged borderline area
of Ka-Ping Yee's IRV simulations (that is, if we were talking about
that particular election as a datapoint in a simulation).  Having
carefully analyzed both Debian 2003 and Burlington 2009, and then read
some of Ka-Ping Yee's research (and played with Nicky Case's wonderful
interactive version), I'm pretty sure that IRV is "stinky cheese" (as
Nicky Case puts it).

r b-j, thanks for advocating for BTR-IRV in Burlington!  These
conversations inspired me to do a little clean up the BTR-IRV/BTR-STV
pages over on Electowiki:
<https://electowiki.org/wiki/BTR-IRV>

Rob
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Re: [EM] Auditing IRV: RAIRE and SHANGRLA

Neal McBurnett-2
In reply to this post by robert bristow-johnson
On Tue, Dec 17, 2019 at 10:41 AM robert bristow-johnson <[hidden email]> wrote:
1. Welcome to the EM list.

Thanks! 
 
2. Although there is a relationship, the issues of Voting Methods (ballot type, FPTP, IRV, Condorcet, Score, Approval...) and Voting Security are not the same.  The only immediate connection between the two issues is that of precinct summability.  FPTP and Condorcet methods are both precinct summable, IRV is not unless you want to count all of the possible ways a ranked ballot can be marked and that is a very large number.
 
Another relationship relates to the question of how to perform a risk-limiting audit: how many paper ballots to audit against the published results, what to do about discrepancies (which do indeed happen), and how to decide when enough sampling and comparison has been done, that the risk of an incorrect outcome has been sufficiently minimized. Different tally methods require different statistical calculations.  This may not be the list to discuss such things on, but knowing where to go for the answers and who is doing the research do seem relevant, thus my message.
 
3. I took a look at the papers you reference and the only real Electrical Engineering aspect of this (one of the papers is IEEE) in my opinion (as an electrical engineer) is that of secure communications.  All that is important, but the auditing thing is just that, recounting ballots.  We do this routinely when the election is close or there is some other funny business.  To that, the only engineering solution, in my opinion are optical scan paper ballots, where the candidate name is on the physical instrument storing the vote (not those punch card butterfly ballots) so that the voter and the auditor see exactly the same ballot and there is no way a voter can think he/she voted for A but the physical instrument appears that he/she voted for someone else.  (If those punch cards were misaligned, you might end up voting for whom you hate the most.)  Regarding secure communications, having total transparency regarding all procedures, including the code use to scan and tabulate ballots, is the key.  It should be public domain and accessible by anyone.

I'm computer scientist and security consultant. The communications issues are indeed important, but so are other aspects.

I doubt it's appropriate to go in to a lot of depth here, but there are indeed other reasons voting systems occasionally interpret and/or tabulate ballots differently than a human would. Humans sometimes circle boxes instead of filling them in, and some state laws require that those be counted as votes. Distinguishing a "hesitation mark" or bit of toner from a marked oval require human eyes. Devices are sometimes configured with the wrong descriptions of the ballot, as happened just last month in Northampton County, PA, causing a huge discrepancy. And even humans sometimes differ on how to interpret a ballot. I've seen them.

Being able to deal with those discrepancies is one of the more challenging aspects of the math behind RLAs. I'm working with Dr Vora at George Washington University on an NSF grant to improve the efficiency of RLAs, a field in which I've worked for nearly two decades, and been invited to testify to a National Academies committee on. You can read their report online at https://www.nap.edu/catalog/25120/securing-the-vote-protecting-american-democracy
 
I was talking with Jim Condos, the Vermont Secretary of State, about this and he said that there is a technology that will digitally photograph each ballot so that if it looks poorly marked, the system can flag a team of election officials, who can immediately pull up the ballot image and look and judge for themselves what the voter intent was.

That can help a lot. But there are a variety of ways that images can be unreliable, as demonstrated e.g. at UnclearBallot: Automated Ballot Image Manipulation - https://mbernhard.com/papers/unclearballot.pdf 
So it is important under many circumstances to look at the paper ballot rather than the image.
 
One thing is, that if the election is in the U.S., the ballot must not, in any manner, be traceable to the identity of the voter who marked it.  If the ballots have serial numbers, those must not be associated with the voter.  That is different from the U.K. and some other democracies.

I dearly wish that was true everywhere in the US, but sadly in a number of states, including North Carolina and Indiana, paperless voting machines allow election officials to connect voted ballots with the voter until after the election day deadline to vote. They do so for the same reason that they do so in the UK: e.g. an early ballot is invalid if the voter dies before election day, and state law says it must not be counted in the tally.
 
4. That said, I don't see what the big deal is.  If you have paper ballots *and* a manual recount is done, there is a way to do IRV manually with piles of ballots.  But it's laborious.  The issue of election security really is unrelated to the issue of whether the Condorcet candidate is elected or not.  Whether a particular IRV election will or will not elect the Condorcet winner is independent of security, redundancy, and auditing issues.  It's only a voting method issue.

Yes, I agree, from the standpoint of the security of the official results of the election. And as I pointed out, there are new ways to audit the results to within a specified statistical risk without a full hand count.

I was just also pointing out that some of us, like the message from Rob that I responded to, do care about other ways tabulating the ballots, and actually run the ballots thru our own tabulation software. That's what caught the attention of folks in Burlington: a different tally method that pointed out the Condorcet winner was different. And when I combine that with the RLA techniques, I find it interesting (but not formally relevant to the official outcome) to understand how close the tally was to other outcomes via various methods.

And in general, as we design voting methods, we should consider how to efficiently audit them.  Colorado law requires a risk-limiting audit of many contests, and the research and software I pointed out make that much easier to do now.
 
5. I am skeptical of the "computers make mistakes" notion. Do you mean a hardware crash?  Because a numerical error with integer arithmetic is not really possible

 I mean software bugs, hardware bugs, errors in specifying tally methods (e.g. as I recall, an analysis of the IRV software in Ireland vs the Irish tally law found that the software didn't perfectly implement the law), security vulnerabilities that allow adversaries to change the results, etc. And when you drill down far enough, cosmic rays can cause memory errors, etc. but we don't need to go that far to know we have problems to solve.

Cheers,
Neal
 
r b-j

> On December 17, 2019 11:07 AM Neal McBurnett <[hidden email]> wrote:
>

> I just joined the list (after a few decades of activity with election methods and auditing). Thanks for the fascinating discussion.  This stuff is even more complicated than I knew.
>
> Let me note one more complication though.  The interpretations by the voting system of the votes ("cast vote records" or CVRs) might
> be wrong, and IRV is famously vulnerable to interpretation errors at each round of tallying.
> Even figuring out how sensitive the outcome of a particular contest is to discrepancies between
> the paper ballots and the CVRs is a challenging computation.
>
> Thankfully, I can also pass on some news of progress in the field: the new RAIRE / SHANGRLA method of auditing IRV elections, which was piloted in the November 2019 election in San Francisco.  Armed with these techniques (and associated open-source code) we should be able to figure out how much error we could tolerate before an IRV tally might end up with a non-Condorcet winner, even though the tally of the official CVRs did pick a Condorcet winner.
>
> And thus there's also more work to be done for any given election method to figure out how to audit it and limit the risk that the outcome is actually incorrect.
>
> Background:
>
> When we declare that a particular election resulted in a particular outcome according
> to a particular algorithm, we are of course trusting that the election system interpreted the human input
> with perfect accuracy and fidelity.  But of course we all know that computers make mistakes and are
> vulnerable to hacking.
>
> Ron Rivest and John Wack invented the concept of Software Independence to deal with that concern.
>
>  Software Independence (Wack and Rivest)
>   http://people.csail.mit.edu/rivest/RivestWack-OnTheNotionOfSoftwareIndependenceInVotingSystems.pdf
>
> The field of Evidence-Based Elections presents a general framework for how to gather evidence to check
> the outcome (set of winners) of a particular contest via software-independent evidence.
>
>  Evidence-Based Elections  -  P.B. Stark and D.A. Wagner
>   IEEE Security and Privacy, Special Issue on Electronic Voting, 2012.
>   http://statistics.berkeley.edu/~stark/Preprints/evidenceVote12.pdf
>
> Evidence-Based Elections employ Risk-Limiting Audits (RLAs) to sample some ballots, compare the paper with the electronic records, and limit the risk of declaring the wrong outcome.  In Colorado, we've pioneered and pushed forward the state of the art in RLAs as I describe here:
>
https://bcn.boulder.co.us/~neal/elections/corla/
>
> But defining RLAs for IRV has been a challenge for many years. Now a better method is available:
>
>  RAIRE: Risk-Limiting Audits for IRV Elections - Michelle Blom · Peter J. Stuckey · Vanessa J. Teague
>   https://arxiv.org/pdf/1903.08804.pdf
>
> It can be used with the new more general RLA approach described in SHANGRLA:
>
>  SHANGRLA: Sets of Half-Average Nulls Generate Risk-Limiting Audits: tools for assertion-based risk-limiting election audits
>   https://github.com/pbstark/SHANGRLA
>
> Which brings me to the post that prompted this post:
>
> On Mon, Dec 16, 2019 at 11:12:24PM -0800, Rob Lanphier wrote:
> > On Sat, Dec 14, 2019 at 7:21 AM robert bristow-johnson
> > <[hidden email]> wrote:
> > > >  So BTR-STV seems like a
> > > > fine compromise, since IRV has failed to pick the Condorcet winner in
> > > > at least one recent public election.
> > >
> > > yes, and i am trying to remind the Progs of that.  but they are not listening.
> >
> > *sigh*.  Yeah, sounds tough.  We had a close mayoral election here in
> > San Francisco in 2018.  Given how close it was, I was really terrified
> > that we'd end up with an election like Burlington 2009.  Thankfully,
> > the IRV elimination order didn't threaten to eliminate the Condorcet
> > winner.  The closeness of the race was between two candidates who
> > probably would have been the final two candidates in a BTR-IRV tally
> > (though the third place candidate wasn't far behind either of the
> > frontrunners).  Given the closeness bitterness of the race, it would
> > have been an electoral reform disaster if any of the top three
> > candidates had lost the way that Andy Montroll did in Burlington (as
> > the Condorcet winner and IRV loser).
> >
> > Rob
>
> Re the 2018 San Francisco mayoral election that Rob alludes to, we can of course use RAIRE / SHANGRLA to audit the winner.
> But he's also interested in whether the winner was a Condorcet winner. Related auditing techniques should be
> able to calculate the minimum number of vote discrepancies that would have resulted in a different Condorcet winner.
> But I don't know of anyone looking at that problem right now.
>
> In general, if we want similar confidence in outcomes for other tally methods, we'll need to come up with RLA methods for them.
> For many of the ranked-choice methods, RAIRE is probably a good model, and it might even provide insights in to other
> aspects of voting methods.
>
> Cheers,
>
> Neal McBurnett                 http://neal.mcburnett.org/

--

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Re: [EM] IRV vs RCV

Kristofer Munsterhjelm-3
In reply to this post by Rob Lanphier
On 17/12/2019 08.12, Rob Lanphier wrote:

> On Sat, Dec 14, 2019 at 7:21 AM robert bristow-johnson
> <[hidden email]> wrote:
>>> On December 14, 2019 2:44 AM Rob Lanphier <[hidden email]> wrote:
>>> I also like Ranked Pairs, but
>>> I suspect that all of the methods that pick a candidate out of the
>>> Smith set are indistinguishable in real-world conditions.  My hunch is
>>> that an analysis of the public elections that had ranked ballots would
>>> reveal that all of them had a single Condorcet winner,
>>
>> except, of course, Burlington Vermont 2009.
>
> I'm pretty sure all of the Condorcet-winner compliant methods chose
> Andy Montroll, given the ballots from the Burlington 2009 election.
> Copeland, Schulze, Ranked Pairs,  etc.  Was there a discrepency
> between Condorcet methods, or just the well-documented discrepency
> between the Condorcet methods and IRV?
>
>>> and therefore
>>> there would be no difference between the results of Ranked Pairs,
>>> Schulze, Tideman, Schulze, or even Copeland.
>>
>> this is the difficult point i have tried to say here.  i think that
>> Schulze is likely the most resistant to voting strategy, but it's
>> too difficult to explain to legislators and the public.>
> Yeah, I agree.  I'm willing to take it on faith that BTR-STV is more
> susceptible to strategy than methods that guarantee Smith set
> membership, but I suspect that Condorcet-compliant methods perform
> better at strategy resistance than standard IRV does.

Doesn't BTR-IRV pass Smith? Suppose that X is in the Smith set and Y is
not. Once X and Y meet in the bottom-two runoff, then by definition of
the Smith set, X beats Y pairwise, so Y is eliminated.

This holds no matter who X and Y are, so a Smith set member can never be
eliminated in a bottom-two runoff when facing a candidate outside the
Smith set. And since every candidate has been subjected to at least one
such runoff, every member outside the Smith set must necessarily have
been eliminated. Thus the method passes Smith.

Or am I missing something? :-)

>> BTR-STV is different.  Schulze, RP, MinMax (dunno about Copeland) all elect the same candidate in the case of an CW or a Smith set of 3.  i don't ever ever ever expect to see a Condorcet RCV ever have a Smith set larger than and i really don't expect to see one without a CW.
>
> Copeland isn't guaranteed to pick a candidate out of the Smith set
> when the Smith set is bigger than one, so it's possible it'll pick a
> different winner than Schulze, RP, MinMax, etc when the Smith set is
> 3.

That also seems wrong. See theorem 1 of
http://dss.in.tum.de/files/brandt-research/choicesets.pdf.
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Re: [EM] IRV vs RCV

Rob Lanphier
Kristofer, I stand corrected on both of the points I was trying to
make (thank you!).  More inline:

On Tue, Dec 17, 2019 at 4:02 PM Kristofer Munsterhjelm
<[hidden email]> wrote:

> On 17/12/2019 08.12, Rob Lanphier wrote:
> > On Sat, Dec 14, 2019 at 7:21 AM robert bristow-johnson <[hidden email]> wrote:
> > Yeah, I agree.  I'm willing to take it on faith that BTR-STV is more
> > susceptible to strategy than methods that guarantee Smith set
> > membership, but I suspect that Condorcet-compliant methods perform
> > better at strategy resistance than standard IRV does.
>
> Doesn't BTR-IRV pass Smith? Suppose that X is in the Smith set and Y is
> not. Once X and Y meet in the bottom-two runoff, then by definition of
> the Smith set, X beats Y pairwise, so Y is eliminated.

Oh, that's delightfully simple!  Your informal proof of BTR-IRV
passing Smith seems correct to me.

I'm now struggling to figure out what the practical benefits of the
other Condorcet methods over BTR-IRV.  Given that BTR-IRV is
reasonably simple to explain, it has an intuitive connection to IRV,
it's hard to understand what the practical benefit is to advocating
for other Condorcet-winner compliant systems.

> > Copeland isn't guaranteed to pick a candidate out of the Smith set
> > when the Smith set is bigger than one, so it's possible it'll pick a
> > different winner than Schulze, RP, MinMax, etc when the Smith set is
> > 3.
>
> That also seems wrong. See theorem 1 of
> http://dss.in.tum.de/files/brandt-research/choicesets.pdf.

Based on what I learned about Copeland back in 1996 when I was first
learning this stuff, I somehow dismissed the usefulness of the
Copeland set, and exhalted the use of the Smith set (since
Smith//Minmax(wv) seemed to be the preferred method discussed on EM
back in 1996, as I recall).  That paper looks like something I should
spend more time reading.

Rob
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Re: [EM] IRV vs RCV

C.Benham
In reply to this post by Rob Lanphier
>   i think that Schulze is likely the most resistant to voting strategy, but it's too difficult to explain to legislators and the public.
> Yeah, I agree.  I'm willing to take it on faith that BTR-STV is more
> susceptible to strategy than methods that guarantee Smith set
> membership, but I suspect that Condorcet-compliant methods perform
> better at strategy resistance than standard IRV does.
>
>
How does BTR-STV not "guarantee Smith set membership" ?      It is a
silly Mickey Mouse method that (at least) pointlessly fails Clone
Independence.

Why do you (Rob)  suspect that all "Condorcet-compliant methods perform
better at strategy resistance than standard IRV does"?

IRV is somewhat more vulnerable to Compromise than Condorcet methods at
the expense of being much more vulnerable to Burial strategy.

43: A
03: A>B
44: B>C (sincere is B or B>A)
10: C

Here A is the sincere and voted  FPP and IRV winner and the sincere
CW.   C is a should-be-irrelevant (say) extreme wing candidate.

Schulze, Ranked Pairs, MinMax, Smith//MinMax using Winning Votes (as
Schulze himself advocates) or Margins (as Robert advocates) as the measure
of defeat-strength all reward the insincere voters (who simply Buried
against the other front-runner, nothing implausibly ingenious) by
electing B.

I rate plain IRV  (where the voters are free to strictly rank from the
top as many candidates as they like and eliminations are one-at-a-time)
as better
than the worst Condorcet methods such as Margins and  "BTR-STV".

Chris  Benham

On 17/12/2019 5:42 pm, Rob Lanphier wrote:

> On Sat, Dec 14, 2019 at 7:21 AM robert bristow-johnson
> <[hidden email]> wrote:
>>> On December 14, 2019 2:44 AM Rob Lanphier <[hidden email]> wrote:
>>> I also like Ranked Pairs, but
>>> I suspect that all of the methods that pick a candidate out of the
>>> Smith set are indistinguishable in real-world conditions.  My hunch is
>>> that an analysis of the public elections that had ranked ballots would
>>> reveal that all of them had a single Condorcet winner,
>> except, of course, Burlington Vermont 2009.
> I'm pretty sure all of the Condorcet-winner compliant methods chose
> Andy Montroll, given the ballots from the Burlington 2009 election.
> Copeland, Schulze, Ranked Pairs,  etc.  Was there a discrepency
> between Condorcet methods, or just the well-documented discrepency
> between the Condorcet methods and IRV?
>
>>> and therefore
>>> there would be no difference between the results of Ranked Pairs,
>>> Schulze, Tideman, Schulze, or even Copeland.
>> this is the difficult point i have tried to say here.  i think that Schulze is likely the most resistant to voting strategy, but it's too difficult to explain to legislators and the public.
> Yeah, I agree.  I'm willing to take it on faith that BTR-STV is more
> susceptible to strategy than methods that guarantee Smith set
> membership, but I suspect that Condorcet-compliant methods perform
> better at strategy resistance than standard IRV does.
>
>
>> BTR-STV is different.  Schulze, RP, MinMax (dunno about Copeland) all elect the same candidate in the case of an CW or a Smith set of 3.  i don't ever ever ever expect to see a Condorcet RCV ever have a Smith set larger than and i really don't expect to see one without a CW.
> Copeland isn't guaranteed to pick a candidate out of the Smith set
> when the Smith set is bigger than one, so it's possible it'll pick a
> different winner than Schulze, RP, MinMax, etc when the Smith set is
> 3.
>
>>>   So BTR-STV seems like a
>>> fine compromise, since IRV has failed to pick the Condorcet winner in
>>> at least one recent public election.
>> yes, and i am trying to remind the Progs of that.  but they are not listening.
> *sigh*.  Yeah, sounds tough.  We had a close mayoral election here in
> San Francisco in 2018.  Given how close it was, I was really terrified
> that we'd end up with an election like Burlington 2009.  Thankfully,
> the IRV elimination order didn't threaten to eliminate the Condorcet
> winner.  The closeness of the race was between two candidates who
> probably would have been the final two candidates in a BTR-IRV tally
> (though the third place candidate wasn't far behind either of the
> frontrunners).  Given the closeness bitterness of the race, it would
> have been an electoral reform disaster if any of the top three
> candidates had lost the way that Andy Montroll did in Burlington (as
> the Condorcet winner and IRV loser).
>
> Rob
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Re: [EM] IRV vs RCV

Kristofer Munsterhjelm-3
In reply to this post by Rob Lanphier
On 18/12/2019 06.15, Rob Lanphier wrote:

> Kristofer, I stand corrected on both of the points I was trying to
> make (thank you!).  More inline:
>
> On Tue, Dec 17, 2019 at 4:02 PM Kristofer Munsterhjelm
> <[hidden email]> wrote:
>> On 17/12/2019 08.12, Rob Lanphier wrote:
>>> On Sat, Dec 14, 2019 at 7:21 AM robert bristow-johnson <[hidden email]> wrote:
>>> Yeah, I agree.  I'm willing to take it on faith that BTR-STV is more
>>> susceptible to strategy than methods that guarantee Smith set
>>> membership, but I suspect that Condorcet-compliant methods perform
>>> better at strategy resistance than standard IRV does.
>>
>> Doesn't BTR-IRV pass Smith? Suppose that X is in the Smith set and Y is
>> not. Once X and Y meet in the bottom-two runoff, then by definition of
>> the Smith set, X beats Y pairwise, so Y is eliminated.
>
> Oh, that's delightfully simple!  Your informal proof of BTR-IRV
> passing Smith seems correct to me.
>
> I'm now struggling to figure out what the practical benefits of the
> other Condorcet methods over BTR-IRV.  Given that BTR-IRV is
> reasonably simple to explain, it has an intuitive connection to IRV,
> it's hard to understand what the practical benefit is to advocating
> for other Condorcet-winner compliant systems.

As Chris Benham pointed out, it fails clone independence. It also
inherits a lot of the compliance failures of IRV (e.g. nonmonotonicity,
no reversal symmetry), and it's not summable. Contrasted with Schulze,
it doesn't tend to elect Minmax winners, and with Ranked Pairs, it fails
LIIA.

I vaguely seem to recall that Warren found out it does worse than
Schulze/RP/etc on Bayesian regret. But I'm not entirely sure of this.



I'm going through the messages of the Condorcet Yahoo group, and it
seems like Alex Small proved something along the lines of BTR-IRV giving
the same winner as Benham with three candidates. Let's see if I can redo
it and make it clearer.

Either we have a Condorcet cycle or there's a CW. If there's a CW, the
equivalence obviously holds. So suppose without loss of generality that
there's an A>B>C>A cycle and that A is the IRV winner. (It's always
possible to relabel the candidates so that this holds.)

When there are two candidates left in IRV, the ultimate IRV winner must
beat the loser pairwise. So given the assumptions above, the full order
must be A>B>C (otherwise, A and C would be in the final round, which
contradicts that A is the IRV winner).

BTR-IRV will first hold a runoff between B and C, and since B beats C
pairwise, B wins. In the next runoff, A wins against B.

Benham will directly eliminate C. In the next round, we have A vs B and
A wins. So the winners are the same.

That seems to show that if you think Smith cycles above three are rare,
then it doesn't matter whether you use Benham or BTR-IRV, because
they'll give the same winner: the CW if there is one, and the IRV winner
if there's a cycle. (Or it almost does: I have to show that the Smith vs
non-Smith runoff rounds don't alter anything.)

But since I'm always adding caveats, BTR-IRV's failure of clone
independence could lead parties to puff up the size of the Smith set in
an attempt to benefit. So if you want a good Smith-IRV hybrid *in
general*, Benham is better.

>>> Copeland isn't guaranteed to pick a candidate out of the Smith set
>>> when the Smith set is bigger than one, so it's possible it'll pick a
>>> different winner than Schulze, RP, MinMax, etc when the Smith set is
>>> 3.
>>
>> That also seems wrong. See theorem 1 of
>> http://dss.in.tum.de/files/brandt-research/choicesets.pdf.
>
> Based on what I learned about Copeland back in 1996 when I was first
> learning this stuff, I somehow dismissed the usefulness of the
> Copeland set, and exhalted the use of the Smith set (since
> Smith//Minmax(wv) seemed to be the preferred method discussed on EM
> back in 1996, as I recall).  That paper looks like something I should
> spend more time reading.

The Copeland set is interesting: for instance, it's a subset of the
uncovered set[1]. However, there don't seem to be any good ways to turn
the set into a proper method that satisfies good properties (clone
independence etc).

[1] E.g. proposition 3.2. of
https://researchportal.port.ac.uk/portal/files/1894394/SELCUK_2010_cright_EL_A_characterization_of_the_Copeland_solution.pdf
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