Re: [EM] Proportional multi-winner ranked voting methods - guidelines?
On 04 Jun 2017, at 11:18, Kristofer Munsterhjelm km_elmet@t-online.de wrote:
On 06/04/2017 10:07 AM, Juho Laatu wrote:
On 04 Jun 2017, at 07:55, VoteFair electionmethods@votefair.org
wrote:
Yes, "proportional multi-winner Condorcet" has no clear,
unambiguous meaning beyond the criteria for identifying the winner
of the first seat.
Yes, it is not easy to say which methods should fall in the
"proportional multi-winner Condorcet" category. I also note that even
if it would be a requirement that the first seat shall go to the
Condorcet winner, if one exists, it is quite possible that the
Condorcet winner would not be elected if there are two seats. (e.g.
when there are two big parties, left and right, and one small
centrist party with a Condorcet winner)
The LCR example is a concrete example that giving the first seat to the CW makes the method fail Droop proportionality. E.g.
43: L>C>R
41: R>C>L
6: C>L>R
number of voters = 90, Droop quota for two seats = 30, so both L and R should be elected, but C is the CW.
For larger assemblies, it might still be a good idea to give a few of the seats to winners chosen by a multiwinner method with few seats, or a single-winner method. Doing so would make centrists the kingmakers in a kingmaker scenario, rather than minor parties on one wing.
I guess we need to decide if we want to violate proportionality or seat monotonicity (if we respect the "first seat to the Condorcet winner" principle). Since the name of the category ("proportional multi-winner Condorcet") includes word "proportional", maybe in this case it is a smaller problem to violate seat monotonicity.
The problems may continue (with smaller probability) in larger assemblies. When the number of seats grows, in LCR examples (with a very small C party) we might elect first {C1}, then {L1, R1}, {L1, C1, R1}, {L1, L2, R1, R2}, {L1, L2, C1, R1, R2}, and eventually {L1, ... , L49, C1, R1, ... , L49}. If L and R have exactly the same number of votes, we may need to elect C1 when the number of seats is odd, no matter how small C party is. C1 will be a kingmaker if we have an odd number of seats, i.e. quite randomly.
Juho
To all.
Of election method, the founders came up with two (more) options: for
counting ranked choice: Condorcet and Borda.
As previously explained, both ways have information value. This group
talks much about the Condorcet route. I chose the Borda route, as
refined by JB Gregory for multi-member PR. My invention of Binomial STV
progresses on that path. BTV does not have the information-loss problems
from irregularities in the count, as discussed in terms of opportunities
for strategic voting.
I would say that BTV short-comings, which it no doubt has, are to do
with the recognised limitations of traditional statistics, more than
anything else. But BTV underlines that elections really are statistical
exercises of the voters indeterminate support for candidates. Altho some
election results are obvious enough. In general, results are not of the
deductive kind: this is the right result. Rather, this more or less
probably is the balance of voters judgment.
from
Richard Lung.
On 02/06/2017 08:23, Kristofer Munsterhjelm wrote:
On 05/22/2017 08:18 PM, VoteFair wrote:
On 5/21/2017 7:10 PM, Armando wrote:
Meanwhile I’ll be thankful for any advice of further readings if you
have.
You, and we, are exploring frontier territory, so there's not a lot of
formal writing about "proportional multi-winner Condorcet" methods
beyond what we've told you about.
If you, or anyone, has specific questions about what I wrote regarding
this topic in "Ending The Hidden Unfairness In U.S. Elections", just
ask.
It's not even all that clear what "proportional multi-winner
Condorcet" means, independent of actual implementations. The lower bar
is "reduces to Condorcet when there's only one winner", but how could
we generalize Condorcet beyond that point? Hard to tell.
Election-Methods mailing list - see http://electorama.com/em for list
info
--
Richard Lung.
http://www.voting.ukscientists.com
Democracy Science series 3 free e-books in pdf:
https://plus.google.com/106191200795605365085
E-books in epub format:
https://www.smashwords.com/profile/view/democracyscience
...
The LCR example is a concrete example that giving the
first seat to the CW makes the method fail Droop
proportionality.
I do not regard Droop proportionality as an important criteria to meet.
It is based on looking at each ballot one candidate at a time, right?
Looking at one candidate at a time is what instant-runoff voting does,
and we know how unfair that can be.
Richard Fobes
On 6/4/2017 1:18 AM, Kristofer Munsterhjelm wrote:
On 06/04/2017 10:07 AM, Juho Laatu wrote:
On 04 Jun 2017, at 07:55, VoteFair electionmethods@votefair.org
wrote:
Yes, "proportional multi-winner Condorcet" has no clear,
unambiguous meaning beyond the criteria for identifying the winner
of the first seat.
Yes, it is not easy to say which methods should fall in the
"proportional multi-winner Condorcet" category. I also note that even
if it would be a requirement that the first seat shall go to the
Condorcet winner, if one exists, it is quite possible that the
Condorcet winner would not be elected if there are two seats. (e.g.
when there are two big parties, left and right, and one small
centrist party with a Condorcet winner)
The LCR example is a concrete example that giving the first seat to the
CW makes the method fail Droop proportionality. E.g.
43: L>C>R
41: R>C>L
6: C>L>R
number of voters = 90, Droop quota for two seats = 30, so both L and R
should be elected, but C is the CW.
For larger assemblies, it might still be a good idea to give a few of
the seats to winners chosen by a multiwinner method with few seats, or a
single-winner method. Doing so would make centrists the kingmakers in a
kingmaker scenario, rather than minor parties on one wing.
Election-Methods mailing list - see http://electorama.com/em for list info
People often talk about Droop proportionality but proportionality for solid coalitions can be Droop or Hare. If a ranked system meets neither, it probably isn't proportional as most people would define it.
From: VoteFair <electionmethods@votefair.org>
To: election-methods@lists.electorama.com
Sent: Sunday, 4 June 2017, 18:27
Subject: Re: [EM] Resume: Proportional multi-winner ranked voting methods - guidelines?
...
The LCR example is a concrete example that giving the
first seat to the CW makes the method fail Droop
proportionality.
I do not regard Droop proportionality as an important criteria to meet.
It is based on looking at each ballot one candidate at a time, right?
Looking at one candidate at a time is what instant-runoff voting does,
and we know how unfair that can be.
Richard Fobes
On 06/04/2017 07:26 PM, VoteFair wrote:
...
The LCR example is a concrete example that giving the
first seat to the CW makes the method fail Droop
proportionality.
I do not regard Droop proportionality as an important criteria to meet.
It is based on looking at each ballot one candidate at a time, right?
Not necessarily. It's a multiwinner generalization of mutual majority.
Mutual majority says: If there's a set of candidates that a majority
ranks ahead of everybody else (but not necessarily in the same order),
then someone from that set should win.
Droop proportionality says: If there's a set of k candidates, and at
least p Droop quotas worth rank all of these ahead of everybody else
(but not necessarily in the same order), then min(k, p) of those should win.
STV passes Droop proportionality just like IRV passes mutual majority.
But Droop proportionality doesn't imply STV (as in the IRV-like method)
more than mutual majority implies IRV. Most Condorcet methods also pass
mutual majority, as electing from the Smith set implies the criterion.
There may be a bit of confusion because methods that pass Droop
proportionality are sometimes called STV methods, e.g. as in Schulze STV.
Perhaps Droop proportionality isn't the exact proportionality measure
one would want - for instance, for my Bucklin methods, I've tried to
base them on divisor methods rather than on hard quotas - but I think
the concept that "some voters who broadly agree on a group of candidates
should see one of them elected" is a good one. That is, that a group of
voters can have "their" seat without having to agree on a strategy.
Although, come to think of it, I think we discussed this before, and you said that that full proportionality for every party is not what you're after - http://election-methods.5485.n7.nabble.com/EM-Proportional-multi-winner-ranked-voting-methods-guidelines-tc34205.html#a34225
From: Toby Pereira <tdp201b@yahoo.co.uk>
To: VoteFair electionmethods@votefair.org; "election-methods@lists.electorama.com" election-methods@lists.electorama.com
Sent: Sunday, 4 June 2017, 18:43
Subject: Re: [EM] Resume: Proportional multi-winner ranked voting methods - guidelines?
People often talk about Droop proportionality but proportionality for solid coalitions can be Droop or Hare. If a ranked system meets neither, it probably isn't proportional as most people would define it.
From: VoteFair <electionmethods@votefair.org>
To: election-methods@lists.electorama.com
Sent: Sunday, 4 June 2017, 18:27
Subject: Re: [EM] Resume: Proportional multi-winner ranked voting methods - guidelines?
...
The LCR example is a concrete example that giving the
first seat to the CW makes the method fail Droop
proportionality.
I do not regard Droop proportionality as an important criteria to meet.
It is based on looking at each ballot one candidate at a time, right?
Looking at one candidate at a time is what instant-runoff voting does,
and we know how unfair that can be.
Richard Fobes
As I was saying before, while Droop proportionality has gained a lot of currency as a criterion, it's just a special case of proportionality for solid coalitions. We could just as easily talk about Hare proportionality. For example, the Sainte-Laguë party list method doesn't obey Droop proportionality, but is seen as more mathematically proportional than D'Hondt, which does obey it. But Sainte-Laguë does obey proportionality for solid coalitions more generally. The point is that Droop proportionality itself is not a deal breaker for a method, and I find it slightly overused.
From: Kristofer Munsterhjelm <km_elmet@t-online.de>
Perhaps Droop proportionality isn't the exact proportionality measure
one would want - for instance, for my Bucklin methods, I've tried to
base them on divisor methods rather than on hard quotas - but I think
the concept that "some voters who broadly agree on a group of candidates
should see one of them elected" is a good one. That is, that a group of
voters can have "their" seat without having to agree on a strategy.
By the way, a sensible Hare version of proportionality for solid coalitions would be that for a faction to be guaranteed s seats, then they should need s - 0.5 Hare quotas (or just over), rather than s Hare quotas. In the single-winner case, this would translate to 50% of the vote. This is what Sainte-Laguë guarantees.
From: Toby Pereira <tdp201b@yahoo.co.uk>
To: Kristofer Munsterhjelm km_elmet@t-online.de; VoteFair electionmethods@votefair.org; "election-methods@lists.electorama.com" election-methods@lists.electorama.com
Sent: Monday, 5 June 2017, 18:09
Subject: Re: [EM] Resume: Proportional multi-winner ranked voting methods - guidelines?
As I was saying before, while Droop proportionality has gained a lot of currency as a criterion, it's just a special case of proportionality for solid coalitions. We could just as easily talk about Hare proportionality. For example, the Sainte-Laguë party list method doesn't obey Droop proportionality, but is seen as more mathematically proportional than D'Hondt, which does obey it. But Sainte-Laguë does obey proportionality for solid coalitions more generally. The point is that Droop proportionality itself is not a deal breaker for a method, and I find it slightly overused.
From: Kristofer Munsterhjelm <km_elmet@t-online.de>
Perhaps Droop proportionality isn't the exact proportionality measure
one would want - for instance, for my Bucklin methods, I've tried to
base them on divisor methods rather than on hard quotas - but I think
the concept that "some voters who broadly agree on a group of candidates
should see one of them elected" is a good one. That is, that a group of
voters can have "their" seat without having to agree on a strategy.
I think that's wrong actually. Forget that last post!
From: Toby Pereira <tdp201b@yahoo.co.uk>
To: Kristofer Munsterhjelm km_elmet@t-online.de; VoteFair electionmethods@votefair.org; "election-methods@lists.electorama.com" election-methods@lists.electorama.com
Sent: Monday, 5 June 2017, 18:19
Subject: Re: [EM] Resume: Proportional multi-winner ranked voting methods - guidelines?
By the way, a sensible Hare version of proportionality for solid coalitions would be that for a faction to be guaranteed s seats, then they should need s - 0.5 Hare quotas (or just over), rather than s Hare quotas. In the single-winner case, this would translate to 50% of the vote. This is what Sainte-Laguë guarantees.
From: Toby Pereira <tdp201b@yahoo.co.uk>
To: Kristofer Munsterhjelm km_elmet@t-online.de; VoteFair electionmethods@votefair.org; "election-methods@lists.electorama.com" election-methods@lists.electorama.com
Sent: Monday, 5 June 2017, 18:09
Subject: Re: [EM] Resume: Proportional multi-winner ranked voting methods - guidelines?
As I was saying before, while Droop proportionality has gained a lot of currency as a criterion, it's just a special case of proportionality for solid coalitions. We could just as easily talk about Hare proportionality. For example, the Sainte-Laguë party list method doesn't obey Droop proportionality, but is seen as more mathematically proportional than D'Hondt, which does obey it. But Sainte-Laguë does obey proportionality for solid coalitions more generally. The point is that Droop proportionality itself is not a deal breaker for a method, and I find it slightly overused.
From: Kristofer Munsterhjelm <km_elmet@t-online.de>
Perhaps Droop proportionality isn't the exact proportionality measure
one would want - for instance, for my Bucklin methods, I've tried to
base them on divisor methods rather than on hard quotas - but I think
the concept that "some voters who broadly agree on a group of candidates
should see one of them elected" is a good one. That is, that a group of
voters can have "their" seat without having to agree on a strategy.
For what it's worth, the CIVS PR method satisfies Droop proportionality,
and it's getting used in practice on a regular basis.
For example, in one recent election to choose the winner of a book
award, the top 5 books were picked and they were #1, #2, #3, #4, and #17
(!) in the nonproportional Schulze ordering. This seemed initially
surprising but made sense because books #5-#16 all had at least one
author in common with #1-#4.
-- Andrew
Toby Pereira wrote:
By the way, a sensible Hare version of proportionality for solid
coalitions would be that for a faction to be guaranteed s seats, then
they should need s - 0.5 Hare quotas (or just over), rather than s
Hare quotas. In the single-winner case, this would translate to 50% of
the vote. This is what Sainte-Laguë guarantees.
From: Toby Pereira tdp201b@yahoo.co.uk
To: Kristofer Munsterhjelm km_elmet@t-online.de; VoteFair
electionmethods@votefair.org;
"election-methods@lists.electorama.com"
election-methods@lists.electorama.com
Sent: Monday, 5 June 2017, 18:09
Subject: Re: [EM] Resume: Proportional multi-winner ranked voting
methods - guidelines?
As I was saying before, while Droop proportionality has gained a lot
of currency as a criterion, it's just a special case of
proportionality for solid coalitions. We could just as easily talk
about Hare proportionality. For example, the Sainte-Laguë party list
method doesn't obey Droop proportionality, but is seen as more
mathematically proportional than D'Hondt, which does obey it. But
Sainte-Laguë does obey proportionality for solid coalitions more
generally. The point is that Droop proportionality itself is not a
deal breaker for a method, and I find it slightly overused.
From: Kristofer Munsterhjelm km_elmet@t-online.de
Perhaps Droop proportionality isn't the exact proportionality measure
one would want - for instance, for my Bucklin methods, I've tried to
base them on divisor methods rather than on hard quotas - but I think
the concept that "some voters who broadly agree on a group of candidates
should see one of them elected" is a good one. That is, that a group of
voters can have "their" seat without having to agree on a strategy.