[EM] MAS defined.

[Jameson Quinn]

I've edited the Chicken Dilemma Criterion article to include the following
introductory text:



> One type of election scenario which is particularly fraught is when there
> is a majority split into two subfactions (below called A and B), competing
> against a united minority (below called C) that is bigger than either of
> the subfactions. This scenario has been called the "chicken dilemma"
> because in many election systems, the two majority subfactions are in a
> situation that resembles the classic "chicken" or "snowdrift game
> (especially if voters are not sure which of the two subfactions is larger).
> That is, if we assume each faction has a single, coordinated strategy
> defined as "cooperate" (vote both candidates A and B above bottom) or
> "defect" (bullet vote, with only the favorite above bottom); and that each
> faction values its preferred choice at 10, its less-preferred choice at 8,
> and candidate C at 0, many voting systems lead to the following payoff
> matrix:
> cooperate defect
> cooperate 9, 9 8, 10
> defect 10, 9 0, 0
> *Fig. 2: Chicken with numericalpayoffs
> <http://wiki.electorama.com/w/index.php?title=Risk_dominance&action=edit&redlink=1>*There
> are various ways to deal with this situation. For instance:
>
>    1. Some voting systems, such as approval voting, ignore the problem.
>    Perhaps the assumption here is that it will be impossible to organize a
>    defection without prompting a retaliation, and thus that both sides will
>    prefer to cooperate. ("Mutual assured destruction"?)
>
>
>    1. Some voting systems, such as Majority Choice Approval
>    <http://wiki.electorama.com/wiki/Majority_Choice_Approval>, try
>    exploit the fact that each faction is not a single coordinated entity, but
>    a group of individual voters. The idea is that if a small number of voters
>    defect, they should be ignored; hopefully, in that situation, majority
>    cooperation will be a stable strategy.
>
>
>    1. Other voting systems, such as ICT
>    <http://wiki.electorama.com/w/index.php?title=ICT&action=edit&redlink=1>,
>    try to exploit the fact that in a real-world election, A and B are never
>    perfectly balanced; one subfaction is always larger. In this case, a voting
>    system can encourage the smaller group to cooperate by threatening to elect
>    C (punishing both groups) if the smaller group defects. The criterion below
>    is passed only by this kind of voting system.
>
>
MAS of course would be in group 2. Personally, I prefer group 2 to group 3,
because group 3 can misread a center squeeze scenario as a failed chicken
dilemma, and decide to "punish" the "betrayers" by electing the true
Condorcet loser.

2016-10-11 6:22 GMT-04:00 Juho Laatu <juho.laatu at gmail.com>:

> I reread the Chicken Dilemma Criterion article in the spirit of "of course
> B should win". To me the weak point in the article seemed to be the
> sentence "The B voters refuse to vote A over anyone". The description did
> not clearly express the underlying assumption that A and B candidates and
> voters actually are very close to each others (similar minded). A voters
> sincerely like B much more than C, and B voters sincerely like A much more
> than C. A and B voters together have majority over the C voters, and
> therefore one of them ("the AB team") should win. Because A is more popular
> than B, A should win. But B voters are strategical and therefore "refuse"
> to vote sincerely, and decide not to rank A above C. In a good election
> method this strategy should preferably not work. There is a risk that both
> A and B voters "refuse" to support B and A respectively (not rank them
> second as they should), and as a result their worst alternative (C) could
> win.
>
> Did this explanation make the philosophy of the "chicken style" criteria
> clearer?
>
> B should not win since if B would win by using this strategy, that could
> encourage also A supporters to do the same, and the whole election could
> become a mess where the winner would be quite random (depending on how many
> voters of each group voted strategically). Note that the number of A and B
> voters could be about the same, and A and B voters would not know which
> group would benefit of applying the "refusal" strategy.
>
> Juho
>
>
>
> > On 11 Oct 2016, at 09:00, Brian Kelly <bkelly1984 at gmail.com> wrote:
> >
> > Hi Jameson,
> >
> > It's always good to see people thinking on these problems and trying
> > to come up with solutions.
> >
> >> MAS is good at dealing with a vote-splitting situation ("chicken
> dilemma"...
> >
> > I've not heard of the Chicken Dilemma before and found a definition at
> > http://wiki.electorama.com/wiki/Chicken_Dilemma_Criterion.  Now I'm
> > more confused because in my opinion, candidate B should win the
> > election described.
> >
> > It is looking to me like the Chicken Dilemma is just a test to see if
> > a voting system is susceptible to bullet voting.  In that case, every
> > system except plurality fails this criteria.
> >
> > Am I missing something?
> >
> > On Mon, Oct 10, 2016 at 10:24 PM,
> > <election-methods-owner at lists.electorama.com> wrote:
> >> Only subscribers are allowed to post to this mailing list.  Please
> >> visit the following location for information on subscribing:
> >> http://www.electorama.com/em
> >>
> >>
> >>
> >> ---------- Forwarded message ----------
> >> From: Brian Kelly <bkelly1984 at gmail.com>
> >> To: The Center for Election Science <electionscience at googlegroups.com>
> >> Cc: election-methods at lists.electorama.com
> >> Date: Mon, 10 Oct 2016 21:24:05 -0700 (PDT)
> >> Subject: Re: MAS defined.
> >> Hi Jameson,
> >>
> >> It's always good to see people thinking on these problems and trying to
> come up with solutions.
> >>
> >>> MAS is good at dealing with a vote-splitting situation ("chicken
> dilemma"...
> >>
> >> I've not heard of the Chicken Dilemma before and found a definition at
> http://wiki.electorama.com/wiki/Chicken_Dilemma_Criterion.  Now I'm more
> confused because in my opinion, candidate B should win the election
> described.
> >>
> >> It is looking to me like the Chicken Dilemma is just a test to see if a
> voting system is susceptible to bullet voting.  In that case, every system
> except plurality fails this criteria.
> >>
> >> Am I missing something?
> >>
> >>
> >>
> >> On Thursday, October 6, 2016 at 12:41:41 PM UTC-6, Jameson Quinn wrote:
> >>>
> >>> I've been working on a simple three-slot system as a next step after
> approval. This has gone through various iterations and names: U/P, MUMA,
> NUMA. The latest, and I hope final, version is MAS, Majority Acceptable
> Score. Here's an explanation, intended for those without a voting theory
> background. The basic system is described in 3 sentences in the first
> paragraph; the second paragraph describes the default rule, which is
> worthwhile but not absolutely essential to the system; and the next two
> paragraphs give some scenarios.
> >>>
> >>> For each candidate, you may upvote, “midvote”, or downvote. Candidates
> with a majority of downvotes are eliminated, unless that eliminates
> everyone. The remaining candidates get 2 points for every upvote and 1 for
> every midvote. Most points wins.
> >>>
> >>> When people leave a candidate blank, that could mean one of two
> things: “never heard of this person”, which should count as a downvote for
> safety; or “no strong feelings”, which should count as a midvote (because
> if the voter really disliked the candidate they would have downvoted). To
> distinguish these possibilities, see if the candidate’s score from
> non-blank votes averages at least half a point per voter; for instance,
> this would be true if they were upvoted by 25%, or explicitly midvoted by
> 50%. If the score is this good, that candidate is reasonably well-known and
> well-liked, so blanks count as midvotes; if it isn’t, that candidate is
> relatively unknown, so blanks count as downvotes.
> >>>
> >>> MAS is good at dealing with a vote-splitting situation ("chicken
> dilemma", so called because in many voting systems it can work like a game
> of chicken between the two majority subfactions). Say that one "side" of
> voters have 55%, but there are two candidates on that side splitting the
> vote and only one on the other side. In this case, assuming voters on
> either side downvote the candidates on the other side, the 45% candidate
> will be eliminated by downvotes, and whichever subfaction of the majority
> has more supporters will win.
> >>>
> >>> MAS also deals well with a "center squeeze" scenario, in which a
> centrist candidate faces off against candidates on either side. Assuming
> all three are equally qualified and likeable, the centrist will probably be
> able to beat either side in a one-on-one race (because leftist voters will
> prefer Center over Right, and vice versa); but it is quite possible that
> there will be more partisans on either side than in the center. In this
> case, the centrist should not be punished simply for being more "crowded"
> ideologically; their ability to dominate one-on-one means they should win.
> But many voting systems, such as IRV, can eliminate the centrist
> prematurely, giving results like the tragic outcome in Egypt 2012.
> Meanwhile, other systems, such as Condorcet, can enable tricky strategies
> by one side to possibly win. In MAS, as long as the center candidate was
> preferred by a respectable number of voters (say, 20% or more), "midvotes"
> from voters in either wing would probably be enough to let the centrist
> win; and either defensive "midvoting" from the weaker wing or defensive
> "downvoting" by the centrists would probably be enough to stop a takeover
> by the stronger wing.
> >>
> >>
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