[EM] MAS defined.

Jameson Quinn jameson.quinn at gmail.com
Thu Oct 6 11:41:19 PDT 2016

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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