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Line 1: Here's the email which introduced the idea of ~~MSDSV,~~ '''majority score declared strategy voting''' ('''MSDSV'''): == Motivation == I've been thinking about strategic rules of thumb in majority score. Basically, the rule I've come up with is: -* Support (top-rate) candidates who are best or comparable to the best; say, above 0.9 on an honest normalized score ballot. -* Reject (bottom-grade) candidates if they're "worse than the average serious candidate". One way to make this precise might be: ifIf you'd prefer a random lottery where first a number ''n'' is picked uniformly among {2,3,5}, then a random lottery is performed among the top ''n'' candidates by honest plurality. Obviously, for an actual rule of thumb, the imprecise wording is better, but I'm just including the precision to help clarify what I mean. -* Assist candidates if they are the best or comparable to the best among serious candidates you are relatively sure will not be eliminated by majority rejection. So, first discount any candidates you think have over 1/3 chance of scoring under 50 or of having over 50% rejection; then re-normalize your honest score ballot for the rest; then assist any candidates who are above 0.9 and whom you're not already supporting. -* Accept the rest. So, basically, simplified further, this rule suggests assisting anyone who you'd otherwise accept, if you think that the candidates you support will all be eliminated. When you put it like that, it looks like a job for a DSV method. Line 20: # Winner is remaining candidate with most support. This is a system that has aspects of [[Bucklin voting]] (majority threshold for eliminations) and of [[IRV]] (eliminate and then ~~retally~~re-tally votes that lost their top-voted candidates). == Properties == Line 30: * Majority, mutual majority (note that MSV does not have MM, IRV does) * Voted majority Condorcet winner? (Neither MSV nor IRV have this property! I am not 100% sure this system has this property, but I'm pretty sure it does at least for 3-candidate elections, and I suspect that it extends to n candidates.) * Voted majority ~~Condercet~~Condorcet loser??? (same qualifications, but I'm less sure) * Voted Condorcet loser (without qualifying by "majority"!) for 3-candidate elections in which all voters use full ballot range (iei.e., at least one candidate each in top and bottom) * Handles CD as well as [[MSV]] * Handles center squeeze better than either MSV or IRV; this is pretty well encapsulated by the VMCW property above. Line 42: Here's my "ideal characteristics" for a political single-winner election system, more or less in descending order of importance: # FBC # Handles center squeeze (iei.e., some form of weakened Condorcet guarantee that's compatible with FBC) # Relatively simple to explain # Minimal strategic burden Line 48: # Handles CD, or at least, CD offensive strategies don't in practice mess up the center squeeze properties. # Some arguable track record SODA does well on 1,2,4, 5, and 6, and horribly on 3 and 7. MSV does well on 1,2,4, and 5, is OK on 3 and 4, and bad on 6. Approval does well on 1,3,4, and 6, is OK on 2, and bad on 4 and 5. MSDSV does well on 1,2,4,5, and 6, and is bad on 3 and 7. Various Condorcet-like methods (MAM, ICT, sorted approval methods) are good on 2, 4, and 6, but none as good as the aforementioned on 1, and all fail 3 and 7. MJ and other Bucklin methods are, as far as I can tell, dominated by MSV on all but 7. And other methods just don't compete. So, MSDSV is on the pareto frontier of the above criteria, which makes it a top-shelf method. Comparison: * SODA does well on 1, 2, 4, 5, and 6, and horribly on 3 and 7. * MSV does well on 1, 2, 5, and 6, is OK on 3 and 4, and bad on 7. * Approval does well on 1, 3, 5, and 7, is OK on 2, and bad on 4 and 6. * MSDSV does well on 1, 2, 4, 5, and 6, and is bad on 3 and 7. * Various Condorcet-like methods (MAM, ICT, sorted approval methods) are good on 2, 4, and 6, but none as good as the aforementioned on 1, and all fail 3 and 7. * MJ and other Bucklin methods are, as far as I can tell, dominated by MSV on all but 7. * And other methods just don't compete. So, MSDSV is on the Pareto frontier of the above criteria, which makes it a top-shelf method. [[Category:Single-winner voting methods]] [[Category:Cardinal voting methods]] [[Category:No-favorite-betrayal electoral systems]]