[EM] Majority Judgement

[Kristofer Munsterhjelm]

On 02/01/2012 06:15 PM, Jameson Quinn wrote:
>
> On 2012 1 31 01:45, "Kristofer Munsterhjelm" <km_elmet at lavabit.com
> <mailto:km_elmet at lavabit.com>> wrote:
>  >
>  > On 01/30/2012 10:09 PM, MIKE OSSIPOFF wrote:
>  >>
>  >>
>  >> Does anyone here know the strategy of MJ? Does anyone here know what
>  >> valid strategic claims can be made for it? How would one maximize one’s
>  >> utility in an election with acceptable and completely unacceptable
>  >> candidates who could win? How about in an election without completely
>  >> unacceptable candidates who could win?
>  >>
>  >> And no, I don't mean refer to a website. The question is do YOU, as an
>  >> MJ advocate, know what MJ's strategy is?
>  >
>  >
>  > A maximally strategic MJ ballot (assuming certainty of all other
> ballots) would be an Approval ballot with a strategic Approval
> threshold, something like "approve of everybody you prefer to the
> frontrunner you like most, then approve of him if he's got lower support
> than the other frontrunner".
>
> Actually, if "maximally strategic" means "favorably changes the margin
> of victory" (the minimum number of ballots that would haved to change to
> change the utility of the outcome), then it only requires voting the two
> distinct frontrunners on opposite sides of the winning median.

I meant maximally strategic in the sense of "most favorably changes the 
outcome in your direction". Voting Approval style should do that because 
it works no matter what the honest median is.

The argument would go something like: say the probability of changing 
the election in a way you prefer, if you vote Approval style, is p_ms 
(for max strategy). Then if you're Homo Economicus, you know that if you 
don't exaggerate maximally, the probability of the change after you 
submit your somewhat-exaggerated ballot is p_ps and p_ps < p_ms. The 
margin here may be really small, but if you're Homo Economicus, you take 
it no matter how small.

I don't think people are Homo Economicus-es, so I agree with you on 
strategy. MJ does degrade more gracefully in this way, too, in that 
those who feel they have to employ some sort of strategy (but don't like 
it) don't have to go all the way, and so don't have to distort as much 
the data MJ uses to find the outcome. I'm just clarifying that (I think) 
Approval-style is the biggest bang for the buck, even if it's not 
realistic.