Hi, I didn't realize Chris' last message to me was posted to the list.
Here is my response to it: --- En date de : Mar 17.6.08, Kevin Venzke <[EMAIL PROTECTED]> a écrit : > De: Kevin Venzke <[EMAIL PROTECTED]> > Objet: Re: [Election-Methods] Reducing 3-cand elections to 8 scenarios > À: "Chris Benham" <[EMAIL PROTECTED]> > Date: Mardi 17 Juin 2008, 13h01 > Hi Chris, > > --- En date de : Mar 17.6.08, Chris Benham > <[EMAIL PROTECTED]> a écrit : > > De: Chris Benham <[EMAIL PROTECTED]> > > Objet: Re: [Election-Methods] Reducing 3-cand > elections to 8 scenarios > > À: "EM" > <[email protected]> > > Date: Mardi 17 Juin 2008, 11h03 > > "A couple of drastic measures that appeal to me > are > > only accepting (and requiring) a first and a second > > preference, > > and to the extent necessary, discarding ballots that > > won't cooperate in voting for the top three > candidates > > (according > > to first preferences)." > > > Kevin, > > I have the same question I had the last time you > proposed a > > method focused on 3 candidates: > > Instead of "discarding ballots", why not > apply > > these methods to the ballots modified by eliminations > > after all but 3 candidates have been IRV-style > > one-at-a-time eliminated? > > The motivation behind the suggestion is different. > > When I proposed SPST I did not realize that IRV could be > used to reduce the field to 3 candidates. I thought this > would violate LNHarm. Simply extrapolating on the method to > allow more than 3 candidates would have violated LNHarm, > although if I had a way to do it, I don't think I would > have been opposed to it. > > At this time, though, my approach is to try to deliberately > create the nomination disincentive that would prevent there > from ever being uncertainty as to who the top 3 candidates > are. I'm reading from FPP's playbook. > > > "Another measure occurred to me: Among the > supporters > > of each of the top three candidates, play "winner > > takes all" > > for the second preference. In other words, all of the > > second preferences from the "A-first" voters > are > > considered to > > be cast for whichever (of the other two candidates B > and C) > > received more. This has a consequence that not giving > > a second preference (if such were allowed) is never > > optimal; your second preference is just determined by > other > > voters > > with the same first preference." > > > With this weird (but I suppose not in principle > > unacceptable) feature, what is the point of > > "requiring a second preference"? > > Two points. > 1. It reduces the probability that the allocation of the > second preferences will be determined based on a very small > number of votes (i.e. because most people voting for some > candidate bullet-voted). That could undermine the perceived > legitimacy of the method. > 2. It increases confidence that everyone will be voting a > preference for two of the three candidates. If supporters > of the two frontrunners (assuming we have two) are allowed > to bullet vote en masse, I suspect that they won't care > much about who the third candidate is. I want voters to be > debating what ranking they're going to vote, not what > candidate. > > One of the big problems with trying to elect compromise > choices, or third place in general, is that you have to get > people to vote for them. > > I'm not sold on the "winner takes all" system > for second preferences being a necessary thing, but I think > it's crucial to have voters believe that if they > don't play along, they're wasting their votes. > > The "winner takes all" thing is a necessary > simplification for my method scheme, though. > > I've managed to implement it in a computer program, > complete with compromise, burial, and monotonicity > checking. There are 6561 possible methods within the > scheme, though only a bit over 2% satisfy my monotonicity > property (i.e. a faction can't make their first > preference win solely by sending some voters home), and > only about a third of those offer some kind of strategy > guarantee to at least one faction. > > Maybe the monotonicity property can be weakened, but > something is definitely necessary to avoid considering > methods like "elect second place." > > It is amazing how most of the "best" methods have > been thoroughly discovered already. I searched for monotonic > methods that had at least some number (3?) of strategy > guarantees, and found six I believe, five of which have > names: Schulze etc., Bucklin etc., FPP, IRV, VFA, and > "elect B if he's the CW; else elect A." > > I found four (very similar) non-monotonic methods that > provide no compromise incentive to either the B or C > factions. No other such methods though. > > I'm currently looking into ways to search for > strategies that are sometimes useful and never harmful when > comparing two scenarios that are close enough to be called > "adjacent" (exactly the same except that two > factions are swapped in relative size). If a faction can > predict that the scenario will be one of the two, and can > assume that no one else will use strategy, they themselves > are free to. > > Kevin Venzke _____________________________________________________________________________ Envoyez avec Yahoo! Mail. Une boite mail plus intelligente http://mail.yahoo.fr ---- Election-Methods mailing list - see http://electorama.com/em for list info
