Re: [EM] Fwd: Go ahead with forward to the Election Methods Listserv
Btw, this is also the approval version of reweighted score voting, so if they adopted it, it would mean that there is an organisation using a limited form of the method. It sounds like it will use 2-3 seat constituencies for any given election, so proportionality might not be that great. Election-Methods mailing list - see http://electorama.com/em for list info
[EM] "Guaranteed Majority criterion" on Electowiki
http://wiki.electorama.com/wiki/Majority_Choice_Approval#Criteria_compliance MCA-AR satisfies the Guaranteed majority criterion , a criterion which can only be satisfied by a multi-round (runoff-based) method. http://wiki.electorama.com/wiki/Guaranteed_majority_criterion The *guaranteed majority criterion* requires that the winning candidate always get an absolute majority of valid votes in the last round of voting or counting. It is satisfied by runoff voting , MCA-AR , and, if full rankings are required, IRV . However, if there is not a pairwise champion (aka CW), there could always be some candidate who would have gotten a majority over the winner in a one-on-one race. Since, unlike most criteria, this criterion can depend on both counting process and result, there could be two systems with identical results, with only one of them passing the guaranteed majority criterion. This is an example of what Mike Ossipoff used to rightfully excoriate as a "rules criterion". To me if "two" voting systems/methods always give the same results with the same impute, then they are really just one method (which perhaps has alternative algorithms) and so they both meet and fail all the same (non-silly) criteria. A voting method criterion should relate to some desirable standard. Is IRV that doesn't allow truncation somehow better that IRV that does? Why can't normal IRV (that allows truncation) just have a rule that says that exhausted ballots in the "last round of counting" are no longer "valid"? Or better yet, since IRV meets Woodall's Symmetric Completion criterion, why can't it include a rule that all ballots are "symmetrically completed" so then the winner in the "final round of counting" will certainly have an "absolute majority of valid votes"? Chris Benham Election-Methods mailing list - see http://electorama.com/em for list info
Re: [EM] "Guaranteed Majority criterion" on Electowiki
Hi Chris, --- En date de : Mer 3.11.10, C.Benham a écrit : >>The guaranteed majority criterion requires that the winning candidate >>always get an absolute majority of valid votes in the last round of >>voting or counting. It is satisfied by runoff voting, MCA-AR, and, if >>full rankings are required, IRV. However, if there is not a pairwise >>champion (aka CW), there could always be some candidate who would have >>gotten a majority over the winner in a one-on-one race. Since, unlike >>most criteria, this criterion can depend on both counting process and >>result, there could be two systems with identical results, with only one >>of them passing the guaranteed majority criterion. > >This is an example of what Mike Ossipoff used to rightfully excoriate as >a "rules criterion". > >To me if "two" voting systems/methods always give the same results with >the same impute, then they are really >just one method (which perhaps has alternative algorithms) and so they >both meet and fail all the same (non-silly) >criteria. Yes, I imagine criteria to be defined based on the results of the method, not the procedure for finding the result... A good reason for this is that there is no objective test for what constitutes a "round of counting" or "getting" a vote in such a round. Or even what is a "valid" vote: It's not obvious that two-vote runoffs should satisfy the criterion. I guess in a "round of voting" the "valid votes" are determined based on the current (i.e. last) round but in a "round of counting" you use all the votes cast and not just those still being evaluated. I can't help but notice that MCA-R or -AR are not even methods, but classes of methods... MCA-AR methods satisfy the criterion purely because they end in a two-round runoff. Why not generalize the article to say that instead?? Kevin Election-Methods mailing list - see http://electorama.com/em for list info
[EM] The MCA page
I thought MCA was supposed to become an umbrella term for MCA and Bucklin. If those in favor of that have backed off of that plan then... good, in my opinion, but then I don't quite get what the plan is. I guess MCA is now a generic term for all median rating methods? The intro paragraph says MCA is a ratings method sometimes called ER-Bucklin. That should probably be fixed since ER-Bucklin is a rank method (or two) and doesn't treat equality the same way as MCA / median rating. Why does the note on terminology say that MCA originally referred to 3-slot MCA-AR-M?? There are not two rounds in standard MCA. The method was just MCA-M. Regarding this: "Clone independence is satisfied along with the weaker and related ISDA by MCA-IR and MCA-AR, if ISDA-compliant Condorcet methods (ie, Schulze) are used to choose the two "finalists". Using simpler methods (such as MCA itself) to decide the finalists, MCA-IR and MCA-AR are not strictly clone independent." First of all how is ISDA weaker than Clone Independence? Neither seems to imply the other. It strikes me as obviously false that using an ISDA method in the runoff will result in the MCA method satisfying ISDA, unless you want to somehow argue that MCA-AR satisfies ISDA when it doesn't require a runoff. Also with Condorcet: How can you say that MCA-AR picks the Condorcet winner when he has majority approval? That doesn't guarantee he will appear in the final runoff. Later-no-help: I'm pretty sure all of the runoff-less MCA methods satisfy this. FBC: Same, but also I don't believe FBC will be retained with any kind of runoff. This page would be a lot better if -IR and -AR were dumped. They are not fully defined, and whatever properties these methods do possess will likely be very different from what standard median rating offers. The categorization of MCA-M, MCA-A, MCA-P doesn't make much sense to me either, unless everybody uses three slots. If you have a 50-slot ballot and the tie is at slot 13, nobody's going to want to use MCA-A or MCA-P. You can break the tie as the score *at* the place where it occurred, or at the slot right before it, or break the tie as Woodall does with QLTD. And any of these methods should result in the same properties being satisfied. Kevin Venzke Election-Methods mailing list - see http://electorama.com/em for list info
Re: [EM] "Guaranteed Majority criterion" on Electowiki
Kevin Venzke wrote: Hi Chris, --- En date de : Mer 3.11.10, C.Benham a écrit : The guaranteed majority criterion requires that the winning candidate always get an absolute majority of valid votes in the last round of voting or counting. It is satisfied by runoff voting, MCA-AR, and, if full rankings are required, IRV. However, if there is not a pairwise champion (aka CW), there could always be some candidate who would have gotten a majority over the winner in a one-on-one race. Since, unlike most criteria, this criterion can depend on both counting process and result, there could be two systems with identical results, with only one of them passing the guaranteed majority criterion. This is an example of what Mike Ossipoff used to rightfully excoriate as a "rules criterion". To me if "two" voting systems/methods always give the same results with the same impute, then they are really just one method (which perhaps has alternative algorithms) and so they both meet and fail all the same (non-silly) criteria. Yes, I imagine criteria to be defined based on the results of the method, not the procedure for finding the result... A good reason for this is that there is no objective test for what constitutes a "round of counting" or "getting" a vote in such a round. Or even what is a "valid" vote: It's not obvious that two-vote runoffs should satisfy the criterion. I guess in a "round of voting" the "valid votes" are determined based on the current (i.e. last) round but in a "round of counting" you use all the votes cast and not just those still being evaluated. A reasonable results-only version would be a criterion that says that if the method is left with two candidates, the one that beats the other pairwise should win. But because we don't know what round of counting or getting a vote means, the criterion must be very weak and say that someone who loses pairwise to everybody else can't win (since there's no way that it would be the victor of a final one-on-one contest), and that's just Condorcet Loser. Looking at that from another angle, we see that the "always elects the winner of a majority" point that IRV proponents like to wave around is also simply Condorcet Loser. If the method passes CL, you can construct a fake elimination order that leads the winning candidate to pass the last round - if it does not, there will be instances where you can't. Election-Methods mailing list - see http://electorama.com/em for list info
