Hi Forest, > De : Forest Simmons <[email protected]> >À : Kevin Venzke <[email protected]> >Cc : em <[email protected]> >Envoyé le : Mercredi 9 octobre 2013 19h51 >Objet : Re: [EM] IA/MPO > >Kevin, > >thanks for working on the property compliances. > >I agree that this method does satisfy the FBC, is monotone, and is at least >marginally clone independent, like Score and ratings based Bucklin and MMPO. > >I am not as expert as you in the various defense criteria. > >My main focus so far is that the method seems to remedy some of the problems >of Approval and some of the problems of MMPO.
Unfortunately, I realized that an SFC problem is possibly egregious: 51 A>B 49 C>B B would win easily, contrary to SFC (which disallows both B and C). But more alarmingly it's a majority favorite problem. >Approval has a problem with this (true preferences) scenario: > >30 A >3 A>C >15 C>A >4 C >15 C>B >3 B>C >30 C > >Of course, (under Approval voting) the two 15 member factions should, and >would bullet C, if they were sure of the numbers, but it is more likely that >due to disinformation from the A and B parties (and other sources of >uncertainty) they would not truncate their second preferences, so A and B >would be tied for most approval. Yes, Approval can't easily adjust on election day if polls were inaccurate or there is a sudden change of sentiment. It tends to settle on two frontrunners, and when it doesn't, the outcome is fairly arbitrary (which isn't better in my opinion). > >However, IA/MPO robustly elects C. > >Our friend MMPO has a problem with > >19 A>B>C >18 B>C>A >18 C>A>B >15 D>A>B >15 D>B>C > 15 D>C>A > >electing the Condorcet Loser D, (unless some preferences are strategically >collapsed). But IA/MPO elects the "right winner" A, with no need to collapse >preferences among members of the ABC clone set.. > >Can you think of any other examples where one or the other of IA or MMPO is by >itself inadequate? Does IA/MPO always improve the outcome in such cases? Well, "implicit approval" as a method on its own wouldn't be proposable, I don't think, due to the majority favorite issue. MMPO isn't fantastic at deterring burial, so I was hoping the IA might address that as in implicit Condorcet//Approval (though plain C//A is not great wrt FBC). Kevin Venzke ---- Election-Methods mailing list - see http://electorama.com/em for list info
