Re: [EM] Juho--Margins fails Plurality. WV passes.
The definition of plurality criterion is a bit confusing. (I don't
claim that the name and content and intention are very natural
either :-).)
- http://wiki.electorama.com/wiki/Plurality_criterion talks about
candidates given any preference
- Chris refers to above-bottom preference votes below
There seems to be (potentially) some sort of an (approval style)
cutoff 1) before the non-listed candidates of each ballot, or 2)
before the least preferred candidates of each voter.
Let's assume the following slightly modified ballots.
11: AB
07: B
12: CA=B
If there are three candidates, A, B and C, then the disapproved
candidates are
- {C}, {A,C} and {} (respectively) with rule 1
- {C}, {A,C} and {A,B} with rule 2
(Note also that existence of a fourth candidate D may have an
impact on which candidates are considered disapproved.)
If the voter given approval to the listed candidates is intentional
then rule 1 seems to be the intended interpretation. Otherwise
interpretation 2 might be correct. Since the cutoff is not explicitly
mentioned, maybe interpretation 2 makes more sense. In this case the
Electowiki definition could read: If the number of voters ranking A
as the first preference is greater than the number of voters ranking
another candidate B higher than last preference, then B must not be
elected.
Juho
On Mar 5, 2007, at 19:49 , Chris Benham wrote:
Michael Ossipoff wrote:
In a posting to a different mailing list, Markus pointed out that
margins fails the Plurality Criterion, and that wv Condorcet
passes the Plurality Criterion.
Yes.
11: AB
07: B
12: C
A Woodall example that applies. Margins elects A, yet C has more
top preference votes than A has
above-bottom preference votes.
Chris Benham
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Re: [EM] Juho--Margins fails Plurality. WV passes.
I'd said: But if we're going to have the added definition-wordiness of Condorcet, we should get what Condorcet can offer, including compliance with the Plurality Criterion, SFC, GSFC, and SDSC, and URNEC. Juho replied: And maybe [will you provide] pointers to the definitions of these too. I reply: Sure, I will. But for right now, I've defined URNEC recenly in an EM posting addressed to you. And I and others posted SFC's definition to EM almost as recently, when a few people were looking for faults in it. But let me start by re-stating URNEC here: A method passes URNEC if, for all situations (configurations of candidates, voters, and voters' preferences) when there is a CW, there is always a Nash equilibrium in which the CW wins and no one reverses a preference. [end of URNEC definition] Approval, Condorcet(wv) and MDDA pass URNEC. Margins, IRV, and Plurality fail URNEC. I may not have recently posted SDSC's defilniltion here, so let me do so now: Strong Defensive Strategy Criterion (SDSC): If a majority prefer X to Y, the they should have a way of voting that ensures that Y won't win,without any member(s) of that majority voting a candidate that they like less equal to or over a candidate that they like more. One votes X equal to Y if one votes X over someone, and votes Y over someone, but doesn't vote X over Y and doesn't vote Y over X. [end of SDSC defilnition] So voting X equal to Y only refers to X and Y that the voter considers good enough to rank. If the voter doesn't vote for X and doesn't vote for Y, s/he isn't voting X equal to Y, as the term is used in the above definiltion. That makes sense, because the candidates who are good enough to rank are the ones that you don't want to demean by votng someone less-liked equal to them. I'll re-post SFC and is supporting definitioins tomorrow. I'd do it now, but there are, as I said, a few supporting definitions, and I've been on the computer for a long time tonight. Mike Ossipoff ___ All new Yahoo! Mail The new Interface is stunning in its simplicity and ease of use. - PC Magazine http://uk.docs.yahoo.com/nowyoucan.html election-methods mailing list - see http://electorama.com/em for list info
Re: [EM] Juho--Margins fails Plurality. WV passes.
Michael Ossipoff wrote: In a posting to a different mailing list, Markus pointed out that margins fails the Plurality Criterion, and that wv Condorcet passes the Plurality Criterion. Yes. 11: AB 07: B 12: C A Woodall example that applies. Margins elects A, yet C has more top preference votes than A has above-bottom preference votes. Chris Benham election-methods mailing list - see http://electorama.com/em for list info
[EM] Juho--Margins fails Plurality. WV passes.
Juho-- In a posting to a different mailing list, Markus pointed out that margins fails the Plurality Criterion, and that wv Condorcet passes the Plurality Criterion. For me, Plurality isn't essential. For instance, I consider MDDA a good proposal. But if we're going to have the added definition-wordiness of Condorcet, we should get what Condorcet can offer, including compliance with the Plurality Criterion, SFC, GSFC, and SDSC, and URNEC. Mike Ossipoff election-methods mailing list - see http://electorama.com/em for list info
