Forgot to say, the simulations used minmax and in usually had three candidates. (different voter groups sizes, e.g. 10% or less or more; different probabilities of ties in preferences)
Juho On Jul 27, 2007, at 2:22 , Juho wrote: > On Jul 23, 2007, at 17:20 , Kevin Venzke wrote: > >> Juho, >> >> --- Juho <[EMAIL PROTECTED]> a écrit : >>> Margins vs. winning votes is another long term discussion topic on >>> this list. There have been many opinions and the final conclusions >>> may be more difficult to draw than in the Range strategy question. >> >> I agree here. >> >>> 1) It can be debated if Condorcet methods are in practice (large >>> scale public elections) vulnerable to strategies. If not, then both >>> margins and winning votes are safe enough and other criteria can be >>> used to pick one of them for use. >> >> It's possible that a coordinated strategy may not be feasible, but >> that >> is not the heart of the problem in my view. >> >> Referring again to this scenario: >> 49 A >> 24 B >> 27 C>B >> >> Under margins the C voters have great favorite betrayal incentive >> without >> any other faction having to use a coordinated strategy. > > Sorry about some delay in answering. > > There certainly are many viewpoints to this scenario. I'll present > one. Please point out if I missed some essential things that you > thought I should answer. > > In this example a single C supporter can indeed change the winner (in > the case of margins) to B by voting B>C instead of C>B. The strategy > is very safe since C supporters can assume that C will not win the > race in any case. > > The pattern that leads to this strategic option is a loop where > - A wins C clearly > - C wins B with a small margin (and low number of winning votes) > - B wins A with an even smaller margin (but high number of winning > votes) > > How about the weak spots then: > - The outcome is not that bad since there is anyway a majority that > would elect B instead of A, and C was beaten too badly to even try to > win (winning votes actually elect B without requiring strategic votes) > - This scenario assumes a natural loop (not very common, and this > type of loop maybe even less common than loops in general) > - It is difficult to find a real world model that would lead to this > kind of votes (what is the reason why voters voted as they did? do > you have a story that would explain this election?) > - Some of the strategic votes could be natural in the sense that if > the numbers above are the outcome of an opinion poll few days before > the election, then some C supporters might give up voting C as their > first option since C seems to be "a sure loser" > > But of course the fact remains that in this scenario margins are more > vulnerable to and encourage strategic voting. The weakest spot of > this scenario is that it seems that it is not very likely to occur in > real life. Maybe there are some variants with more credible "real > life" numbers. > > This problem is margins specific but so far I couldn't find the > reasons why this would make margins generally fail (worse and with > higher probability than winning votes) in real life (large scale > public) elections. I gave some links to the winning votes problems > cases. They (for example) seemed more probable in real life to me > than this scenario. But I have not done a complete enough analysis to > claim that margins would definitely beat winning votes and that the > probability of this scenario would be low enough not to be a threat. > >>> 2) There are as well cases where winning votes are more >>> vulnerable to >>> strategies than margins. So the question is not one-sided. >> >> However, it is pretty clear that margins has a worse FBC problem than >> WV does. Simulations have shown this, but it can be argued >> logically as >> well. > > May be so. Is there some reason why FBC would be a key criterion in > this case? I made some time ago some simulations on margins and > winning votes on if some certain random voter group or any of the > voter groups could (from their point of view) improve the outcome of > the (sincere) election by voting strategically (in whatever way). The > simulation gave margins somewhat better results than to winning > votes. Maybe the results depend a bit on what one simulates. > >> If margins outperforms WV in some respect, I'd like to be able to >> state >> exactly how. > > - to me the choices that margins make with sincere votes seem (not > necessarily perfect for all needs but) clearly more sensible than the > choices of winning votes > - some of the scenarios where winning votes have strategic problems > appear to be more probable in real life than the problem scenarios of > margins (this feeling is however based on only a limited number of > cases and not a thorough analysis) > - margins are easy to explain and understand and justify to the > voters/citizens => "least number of additional votes needed to win > all the other candidates" (no need to talk about breaking loops and > about complex algorithms) > > Sorry about not providing any more exact answers. The first > explanation above is very obvious to me. The second case is just an > estimate. The third one is again a fact although "social and > psychological" by nature. > > I've often seen some formal properties of voting methods presented as > final proofs of the superiority/inferiority of some particular > method. I don't measure the benefits as number of proven theorems. > Especially in Condorcet methods the problem cases are typically > related to scenarios that are not very common in real life. Therefore > I'd like to see the claims linked to real world examples that > demonstrate the theoretical scenarios in real life situations and > estimate their probability, harmfulness, ease of applying them, risk > of backfiring strategies etc. > > Juho > >> Kevin Venzke >> >> >> >> _____________________________________________________________________ >> _ >> _______ >> Ne gardez plus qu'une seule adresse mail ! Copiez vos mails vers >> Yahoo! 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