Majority score voting: Difference between revisions
Category:Graded Bucklin systems → Category:Graded Bucklin methods
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# '''Voters can support, assist, accept, or reject each candidate. Default is accept. Candidates get 2 points for each percent of "support" and 1 point for each percent of "assist", for a total of 0-200 points. '''
#*''Obviously, you should support the best candidates (perhaps a quarter of them), and reject the worst (perhaps half of them). For the rest, the
# '''Eliminate any candidates rejected by over 50%, unless that leaves no candidates with over 50 points.'''
#* ''If possible, the winner shouldn't be somebody opposed by a majority. But this shouldn't end up defaulting to a candidate who couldn't at least get accepted by over 1/2 or supported by over 1/4.''
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#* ''This finds the candidate with the widest and deepest support.''
== Naming and relationship to other systems ==
Note: Majority score voting was originally called SARA voting, an acronym for the 4 ratings voters can give. However, putting these ratings out-of-order is confusing, even if it results in a nice-sounding acronym.▼
▲
It's also similar to other systems such as [[MAS]], [[Majority Choice Approval]], and other [[graded Bucklin]] systems. Like such systems, it first checks a candidate's median, and, if that is good enough to be comparable with other candidates, goes on to break that "tie" using some other voting method.
== Criteria compliance ==
Majority score passes the [[favorite betrayal criterion]], the [[majority criterion]], [[Independence of irrelevant alternatives]], [[Local independence of irrelevant alternatives]] (under the assumption of fixed "honest" ratings for each voter for each candidate), [[Independence of clone alternatives]], [[Monotonicity]],
There are a few criteria
* It fails the [[mutual majority criterion]], but passes if the mutual majority in question unanimously rejects all candidates outside their mutually-preferred set. It also passes if the number who give the strongest candidate in the set a rating below "support" is less than three times the amount by which the overall group exceeds 50%.
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* It fails the [[participation criterion]] but passes the [[semi-honest participation criterion]].
* It fails the [[Strategy-free criterion]], but, as shown in the center squeeze scenario below, in a 3-candidate scenario it does at least offer viable strategies to each of the subgroups of the majority that prefers X>Y, such that either of the potentially-strategic subgroups has a strategy to ensure Y loses, even if the other potentially-strategic subgroup does not maximally cooperate. ("Subgroup" in this sense is characterized by whether they prefer Z over or under both. The assumption is that the "honest" vote is Support, Accept, Reject in some order for the three candidates, or only Support and Reject in case of indifference between two of them. This guarantees that any X>Z>Y voters will maximally cooperate under honesty, so this subgroup is not potentially-strategic.)
It fails the [[consistency criterion]], the [[Condorcet loser criterion]], the [[majority loser criterion]], and the [[later-no-harm criterion]].▼
▲It fails the [[consistency criterion]], the [[Condorcet loser criterion]], [[reversibility]], the [[majority loser criterion]], and the [[later-no-harm criterion]].
== An example ==
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Note that A, the bigger of the two subfactions, must necessarily be above the 50-point threshold in step 2, so Z will be safely eliminated. In many cases, B, the smaller subfaction, will fall short of 50 points. This helps explain the rationale for putting that threshold at 50 points.
This is not to say that majority score solves the chicken dilemma 100%.
As a final tricky scenario, consider what happens in the above case if the minority Z prefers the smaller subfaction B. That results in a [[center squeeze]] scenario: one where candidate B is a [[Condorcet winner]] (able to beat either rival in a one-on-one race) but an honest plurality loser (with the smallest faction of direct supporters). This is more common than one might think; candidate B is fighting an ideological battle on two fronts, while candidates A and C are free to triangulate towards the middle without losing supporters, so the fact that B has the smallest direct support may not reflect a lack of quality. Thus, generally speaking, as long as each faction considers their second choice to be more than half as good as their first choice (taking the worst choice as 0), it's pretty clear that the Condorcet-winner candidate B is the one who democratically "should" win this election.
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One interesting aspect in the above three scenarios: "assist" is only strategically favored in the case of a center squeeze scenario, when the A and C voters are helping B, whom they see as the the "lesser evil", beat the other extreme. If there isn't a center squeeze, voters need only use "support", "accept", or "reject". In fact, even in center squeeze, voters could get by without "assist", as long as enough A and C voters were willing to support B outright. So eliminating the "assist" option would not substantially change the strategic outcome; but it would reduce the expressive power available to the A and C voters in a center squeeze scenario. Thus majority score sacrifices some possible extra simplicity in return for this increased expressive power.
It is very rare to have a voting system which can deal with both chicken dilemma and center squeeze. The two situations are very similar, even when voted honestly, and yet the "correct" outcome is different. And under strategic voting in many voting systems, it is very easy for the two different scenarios to lead to identical ballots. Delegated voting systems such as [[SODA voting]] can deal with both; but without that kind of explicit participation in the voting process from the candidates, it is very hard to find a system which deals with both types of scenario better than majority score does.
=== Worst case? ===
Majority score could still get a "wrong" answer in cases of a multi-way Chicken dilemma, such that none of the subfactions reached 25%. This scenario is avoidable if the subfactions compensate by "assisting" each other's candidates, but that cooperation is subject to slippery-slope chicken dynamics.
If this highly-specific scenario is the most-plausible worst case, it would seem that majority score is a pretty good system.
== As the first round of a two-round system ("majority score with runoff") ==
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== Relationship to NOTA ==
As discussed in the above section, if all the candidates in the first round got a majority "reject", then the voters have sent a message that none of the candidates are good, akin to a result of "[[none of the above]]" (NOTA). Majority score still gives a winner, but it might be good to have a rule to limit the chance that such a winner would remain in office for multiple terms. This could either be a hard term limit, so that such a winner could only legally serve one term; or perhaps a softer rule that if they run for the same office again, the information of what percent of voters had rejected them should be next to their name on the ballot.
[[Category:Graded Bucklin
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