Expanding Approvals Rule: Difference between revisions
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In the example, {e1, e2, e3} is the outcome of QBS. Although PSC is not violated for voters in {1, 2, 3} but the outcome appears to be unfair to them because they almost have a solid coalition. Since they form one-third of the electorate they may feel that they deserve that at least one candidate such as c1, c2 or c3 should be selected. In contrast, it was shown in Example 5 that EAR does not have this flaw and instead produces the outcome {e1, e2, c1}.</blockquote> |
In the example, {e1, e2, e3} is the outcome of QBS. Although PSC is not violated for voters in {1, 2, 3} but the outcome appears to be unfair to them because they almost have a solid coalition. Since they form one-third of the electorate they may feel that they deserve that at least one candidate such as c1, c2 or c3 should be selected. In contrast, it was shown in Example 5 that EAR does not have this flaw and instead produces the outcome {e1, e2, c1}.</blockquote> |
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== Monotonicity == |
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EAR fails the monotonicity criterion.<ref>{{cite web|url=http://lists.electorama.com/pipermail/election-methods-electorama.com/2018-February/001682.html|title=Path dependence monotonicity failure in BTV|website=Election-methods mailing list archives|date=2018-02-18|last=Munsterhjelm|first=K.}}</ref> |
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The example has two factions support two candidates each (e.g. one faction supports candidates X and Y, and another candidates W and Z), where X and W are almost exactly tied. In the original two-seat election, X wins and then the other winner must come from the WZ coalition, so Z wins. Then Z is raised on a X>Z ballot, which makes W win the first seat instead. Now the second winner must come from the other coalition, and so Y wins: raising Z makes Z lose. |
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== Notes == |
== Notes == |
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