Peter Zbornik ~
Here are answers to your questions (which are copied below).
In VoteFair representation ranking, the winner of position # 1 is
identified using VoteFair _popularity_ ranking, which is equivalent to
the Condorcet-Kemeny method. That single-seat algorithm is explained in
Wikipedia.
Chapter 15 of "Ending the Hidden Unfairness in U.S. Elections" explains
(step-by-step) how VoteFair _representation_ ranking identifies the
winner of the seat in position # 2. The explanation includes a specific
example. Here is a link to a PDF file that contains just that chapter:
http://www.solutionscreative.com/downloads/EHU_RepRankingOnly.pdf
The example in that chapter is presented graphically. Below are the
same ballot preferences expressed using a more familiar syntax (for this
forum). There are 100 ballots, and each group of 10 ballots have the
same ranking.
A=Aletha, E=Elliot, M=Meridith, R=Roland, S=Seldon, W=Walter
S, E, M, W, R, A x10
S, E, M, W, A, R x10
S, E, W, M, A, R x10
S, M, W, E, R, A x10
S, M, E, A, W, R x10
S, M, E, W, R, A x10
S, M, E, W, A, R x10
A, W, R, S, M, E x10
R, A, W, M, S, E x10
R, W, A, M, E, S x10
In this example S (Seldon) wins position # 1, and W (Walter) wins
position # 2.
Notice that W would not win the second position if overall popularity
were being calculated. (That would be M or E, depending on the method
used.)
Also note that -- unlike STV (and IRV) -- the calculations do not look
at just the currently-considered top-ranked candidate. Instead, the
calculations look "deep" into the ballot ("looking" all the way to the
bottom of each ballot if necessary).
In conventional terms, S is the most popular "majority" candidate, and W
is the most popular "opposition" candidate.
Expressed another way, W is not the second-most "popular" among all the
voters. Instead, W is the most popular among the voters who are not
well-represented by the first-position winner (S).
Additional consideration is given to the "majority" voters if they
amount to more than just 51% (or so). For example, if a majority of 70%
of the voters have the same preferences, their secondary preferences are
"squeezed" into 20% (the amount beyond 50%) when they are combined with
the remaining not-yet-represented 30% of the voters.
The supplied chapter explains yet another consideration that ensures
that the majority cannot rank a variety of minor (unpopular) candidates
at the top of their ballot to make it look like they are unrepresented
by the first-position winner.
The details are explained, step by step, in the supplied PDF-format chapter.
One organization that uses VoteFair ranking to elect its officials has
two locations for its members. VoteFair representation nicely ensures
that neither location outvotes the other location. So far the results
I've seen give the same results for both VoteFair popularity ranking and
VoteFair representation ranking, so their membership is not as divided
as it might otherwise seem. The organization has been very happy with
the results. There is a testimonial on the VoteFair site.
More broadly, in the many cases where VoteFair ranking is used, the
winner of position #2 is often the same as the second-most popular
according to VoteFair popularity ranking (equivalent to Condorcet-Kemeny).
Yet I have also seen numerous cases where VoteFair representation
ranking does produce a result that is different (in the second position)
from VoteFair popularity ranking. Such results reveal a significant
"split" in the voter preferences. Specifically the method has been
successful in identifying who deserves to win the second-most
representative position when the second-most popular (according to
VoteFair popularity ranking) is not the right choice (because that would
allow the same majority to fill both positions).
Regarding positions # 3 and # 4 and beyond, VoteFair representation
continues the ranking process by repeating the
"majority-versus-opposition" algorithm for each pair of next-most
representative positions.
When I designed it I assumed that in many cases only the top two most
representative candidates would need to be identified. That's because
other methods can be used to fill other seats. For example, different
districts can be used to fill other seats in a legislature, and VoteFair
party ranking can fill seats on a PR or PR-like basis (which requires
that party preferences be marked on the ballot).
In your situation the winners are filling an (open) party list, and you
do not know how many party-list seats will be won. You have said that
you expect that the number might be 1, 2, 3, 4, or 5 seats. For this
purpose VoteFair representation ranking would fill position # 1 with the
overall most popular "majority" candidate, and would fill position # 2
with the overall most popular "opposition" candidate, and would fill
position # 3 with the next-most popular "majority" candidate, and would
fill position # 4 with the next-most popular "opposition" candidate.
The code that implements VoteFair representation ranking is open source
code, so "a complete and exhaustive description of the algorithm" is the
code itself, which is well-commented:
http://github.com/cpsolver/VoteFair-ranking/blob/master/VoteFairRanking.pm
(The code also handles "ties," which is necessary for an "exhaustive
description of the algorithm." The explanation in the supplied chapter
is also quite complete, although it does not deal with how to handle
"ties.")
Although the code is written in Perl, it uses a subset of Perl that
makes it straightforward to port the code to the "C" language.
(The code just handles numbers because the Vote-Info-Split-Join (VISJ)
software is available to handle text, such as the names of the candidates.)
Getting back to the VoteFair ranking algorithm, if you would like to see
details about the calculations without downloading and running the
software, please supply me with a specific example (in the above format
if there are more than just a few ballots), and I can run the VoteFair
ranking software and have it produce a "log" that I can post here.
In your party-list situation, when you reach the point where
gender-based quotas are no longer likely to displace any of the
candidates who -- without the quota adjustments -- would win positions #
1, # 2, # 3, and # 4, then I can add code (for "VoteFair party-list
ranking") that better calculates the winner of position # 5 and beyond.
In that case you can think of position # 5 as being filled by a
candidate who represents 20 percent of the voters who are not
well-represented by the winners of the first 4 positions. That
enhancement would amount to moving a portion of the VoteFair
_negotiation_ ranking code into the VoteFair ranking code that is on
GitHub. For that purpose it would be necessary to specify a threshold
to determine at what seat/position a minority is large enough to win a
seat/position.
In summary, the result of using VoteFair representation ranking,
combined with shifting the most-popular women into positions # 2 and/or
# 5 if necessary (to meet that quota), would meet your desire for a
method "which allows quoted seats to be proportionally distributed, in
order to avoid that the same voters get all quoted seats."
If the algorithm for VoteFair representation ranking still isn't clear
after reading the supplied chapter (in PDF format), please ask questions.
Thank you for your interest.
Richard Fobes
On 2/28/2013 11:37 AM, Peter Zbornik wrote:
Dear Richard,
sorry for not getting to your reply earlier than now.
Comments to your email in the text below.
2013/2/17 Richard Fobes<[email protected]>:
On 2/17/2013 12:17 AM, Peter Zbornik wrote:
2013/2/16 Kristofer Munsterhjelm<[email protected]>:
On 02/14/2013 07:07 PM, Richard Fobes wrote:
...
... as in
the top-down method of Otten?
...
... perhaps Peter meant this one?
http://www.votingmatters.org.uk/ISSUE13/P3.HTM
yes, that's the method I was thinking of. Thanks Kristofer.
The approach specified in this article by Joseph Otten involves identifying
"doomed" candidates and "guarded" candidates.
No, VoteFair representation ranking does not use that approach.
VoteFair representation ranking uses a more advanced approach that looks
deeper into the ballots.
Specifically, after the first-position winner has been chosen, VoteFair
_representation_ ranking starts by identifying the ballots that do not rank
that candidate as their first choice, and using those ballots it identifies
which (remaining) candidate is most popular. Then, it looks at the relative
ranking between those two candidates.
Obviously the ballots that rank the first-position winner higher are
well-represented. The other ballots -- that rank the second tentatively
popular candidate above the first-position winner -- are not represented by
the first-position winner, so those ballots get full influence. The
well-represented ballots get only a small influence, specifically to the
extent that the first winner had the support of _more_ _than_ half the
voters (the amount beyond 50%). Then the second-position winner is
identified.
I don't understand votefair ranking neither from the description above
nor from the web pages.
Don't you have a worked example and a complete and exhaustive
description of the algorithm?
Note that the second-position winner might be, or might not be, the
tentatively identified candidate.
This approach precludes the strategy of a majority of voters putting
unpopular candidates at the top of their ballot (with different voters using
different unpopular candidates) as an attempt to fool the algorithm into
thinking they are not well-represented by the first-position winner.
This approach avoids the weakness of STV (and IRV), which focuses attention
on the top-ranked candidate on each ballot, and only looking at lower-ranked
candidates on an as-needed basis.
Possibly combined in some way with
http://www.votingmatters.org.uk/issue9/p5.htm .
Maybe, I don't know.
The key paragraph from this second article is:
"Were we to know in advance that we would win, say, n seats in a region,
then it would be straightforward to use STV to select n candidates from the
potential candidates and put them in the top n places in our list. If we
don't know n in advance (which we don't!) then we can perform this operation
for every possible n, i.e. from 1 up to the number of seats available in the
region, and attempt to construct a list whose top n candidates are those
victorious in the nth selection ballot. (There is really only 1 ballot - the
division into n ballots is notional.)"
It says what I said earlier: that STV needs to know in advance how many
seats will be won.
I did not quickly understand how Joseph Otten proposes combining the
different lists (one for each value of "n") into a single list, and I'm not
in the academic world so I would not get paid to spend time figuring that
out, and since Peter says it may not be relevant, I'll leave this level of
detail unresolved.
Getting to the point of answering Peter's question, no, VoteFair
representation ranking also does not use this second-article approach.
Shifting perspective here, there is an important difference between STV and
VoteFair representation ranking.
STV has the same weakness as IRV, namely it puts all of its focus on the
top-ranked candidate on each ballot.
In contrast, VoteFair representation ranking looks much deeper into each
ballot to identify whether the ballot is from a voter who is (or is not)
well-represented by which candidates have won the earlier seats (in the
party list).
Well I don't understand what "looking deeper" means.
As I've indicated before, if a party list needs to be longer than about five
positions, it's possible to get even better proportionality in the later
seats by using an algorithm used in VoteFair _negotiation_ ranking.
The algorithm behind VoteFair _negotiation_ ranking could calculate a full
party-list ranking, and then if the ranking violates the gender-based rules,
then an administrator can indicate an "incompatibility" that adjusts the
ranking to meet the gender-based quota (expressed as an incompatibility).
There are two reasons why I haven't proposed using VoteFair negotiation
ranking for use in a party-list election:
* It is not designed to handle thousands of voters, which would be needed
for party-list voting. (It's designed for a group of people working in a
collaborative situation.)
Party list voting will have max 500 voters, typically less than 100.
* It is designed in a way that regards the different party-list positions as
distinct "proposals" (such as filling cabinet positions) rather than as
somewhat-equivalent seats being filled.
Yet, as I've indicated, the advanced adjustment capabilities of VoteFair
_negotiation_ ranking can be combined with VoteFair _representation_
ranking. That would create a "VoteFair party-list ranking" algorithm.
However, combined with the need for gender adjustments in up to two
positions, that algorithm would only start having significantly different
results starting at about the fifth seat. That makes it not worthwhile for
this situation that involves five seats, with a high likelihood that the
fifth-position winner will be displaced to fulfill a gender-based quota
requirement.
As I mentioned, I am looking for an algorithm, which allows qouted
seats to be proportionally distributed, in order to avoid that the
same voters get all quoted seats.
In the future when longer party lists are needed, adjustments can be made
starting at about the fifth seat to provide representation for small --
although not tiny -- minorities.
If we expect the party to win only 1, 2, 3, 4, or 5 seats, the first four
positions need to be filled by:
1: The overall most popular "majority" candidate
2: The overall most popular "opposition" candidate
3: The next-most popular "majority" candidate
4: The next-most popular "opposition" candidate
That's what VoteFair representation ranking calculates -- in a way that
deeply looks into the ballots to ensure representation for
not-yet-represented voters.
Richard Fobes
Best regards
Peter Zborník
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