[EM] [CES #8922] Score Voting and Approval Voting not practically substantially different from Plurality?

[Kevin Venzke]

Hi Benn,


>________________________________
> De : Benjamin Grant <panjakrejn at gmail.com>
>À : Kevin Venzke <stepjak at yahoo.fr> 
>Cc : em <election-methods at electorama.com> 
>Envoyé le : Lundi 24 juin 2013 12h11
>Objet : Re: [EM] [CES #8922] Score Voting and Approval Voting not practically substantially different from Plurality?
>
>On Mon, Jun 24, 2013 at 12:50 PM, Kevin Venzke <stepjak at yahoo.fr> wrote:
>
>
>>>But you can change the scenario so that Plurality would be failed:
>>>>
>>>>51: C1 rated 5, C2 unrated
>>>>49: C2 rated 10, C1 unrated
>>>>
>>>>Kevin
>>>>
>>>
>>>A little confused again.  What voting system are we using above? Lost track of that.
>>
>>
>>My assumption was that we were talking about Range, with blank ratings counting as zero.
>>
>>Kevin
>>
>>
>
>If we are talking about Range and counting blank rating as zero, then this:
>
>
>51: C1 rated 5, C2 unrated
>49: C2 rated 10, C1 unrated
>
>is really no different than this:
>
>
>51: C1 rated 5, C2 rated 0
>49: C2 rated 10, C1 rated 0
>
>And I think, since plurality says ""If there are
>two candidates X and Y so that X has more first place votes than Y has any place 

>votes, then Y shouldn't win", then X and Y have the same number of "any" place votes, 

>i.e., Range voting can NEVER fail plurality. Again, I can't imagine a decent system 

>that would.

Woodall's framework involves a concept of voters explicitly acknowledging candidates on their ballots, and Plurality is based on this. It doesn't really matter whether being unrated or being rated 0 are treated the same by the method. Personally I think a "0" rating is about the same as not being acknowledged as having any value, but if instead we say that an explicit "0" rating counts as the acknowledgment, then Plurality failures can be avoided as long as the voters put "0"s instead of leaving candidates unranked.

>Now if there was some functional difference between a 0 rating and no rating at all, 

>we could examine that, I think.

The functional difference for Plurality relates to the input, not the result. Consider why this criterion should be of any interest in the first place. You seem to agree that it is not good to fail it.

>In any case, with a Range/Score system that permits people to have a functionally 

>different from zero "no rating" option, I still have an issue concluding the the 

>Plurality criterion was failed.  Did C1 have more "first place" votes than C2? I 

>don't think so.
...
>
>What am I missing?  Or have I screwed up somewhere?


What "first place votes" means in the rank context is "strictly ranked above all of the other candidates." Plurality is originally defined for rank methods. If you want to apply criteria for rank methods to some other kind of method, you have to explain how you can interpret the latter as a rank method. For ratings ballots I think it's easiest to say that you just extract the relative rankings from the ratings.

Kevin