Proportionality for Solid Coalitions: Difference between revisions
Proportionality for Solid Coalitions (view source)
Revision as of 16:17, 19 February 2020
, 4 years agoref formatting with Citer
Psephomancy (talk | contribs) (add references tag) |
Psephomancy (talk | contribs) (ref formatting with Citer) |
||
Line 45:
|}
Looking at the top 5 lines, 50 voters, a Hare quota, mutually most prefer the set of candidates (A1-5) over all other candidates, so Hare-PSC requires at least one of (A1-5) must win. (Note that Sequential Monroe voting fails Hare-PSC in this example. However, one could forcibly make SMV do so by declaring that the candidate with the highest Monroe score within the set (A1-5) must win the first seat, for example.) <ref name="The Center for Election Science 2020">{{cite web | title=An example of maximal divergence between SMV and Hare-PSC | website=The Center for Election Science | date=2020-01-31 | url=https://forum.electionscience.org/t/an-example-of-maximal-divergence-between-smv-and-hare-psc/586 | access-date=2020-02-19}}</ref>
Generally, Droop-PSC makes it more likely that a majority will win at least half the seats than only Hare-PSC. The reason for this is that majority solid coalitions always constitute enough Droop quotas to always win at least half the seats, while with Hare quotas they can only guarantee they will win just under half the seats and have over half a Hare quota to win the additional seat required to get at least half the seats. 5-winner example using STV with Hare quotas:
Line 71:
Note that 51 voters, a majority, prefer (A1-3) over all other candidates, and thus electing all 3 of them would mean 3 out of 5 seats, a majority, would belong to the majority. Also, the Droop quota here is 17, and thus by Droop-PSC the majority has 51/17=3 PR guarantees, which would give them a majority of seats. However, by Hare-PSC, they only have 51/20 rounded down = 2 PR guarantees, and thus by Hare-STV:
<blockquote>So, the Hare quota here is 20. A1 and A2 are immediately elected, but post-transfer A3 only has 11 votes, and is thus eliminated first. B1, B2, B3 take the remaining 3 seats.<ref name="reddit 2011">{{cite web | title=Can Ranked-Choice Voting Save American Democracy? : EndFPTP | website=reddit | date=2011-01-26 | url=https://www.reddit.com/r/EndFPTP/comments/ermb1s/comment/ff7a7f8 | access-date=2020-02-19}}</ref></blockquote>
There can be quota overlaps when assigning PSC claims; suppose a group constituting 80% of a quota of voters vote A>B>C=D, another group of 80% of a quota vote B>A>C=D, and another group of 50% of a quota vote C>A=B=D. Then, 2 candidates must be elected from the set (A, B, C, D), since in total 2.1 quotas mutually most prefer that set, but a further constraint is that 1 candidate must win from within (A, B), since 1.6 quotas mutually most prefer them. It would not satisfy PSC if the final winner set had neither A or B in it in other words, even if it had C and D.
| |||