[EM] 3 or more choices - Condorcet

[Kevin Venzke]

Hi Juho,



----- Mail original -----
> De : Juho Laatu <juho4880 at yahoo.co.uk>
>>  I don't believe the public needs to understand the terms 
> "plurality criterion"
>>  or "implicit approval" or even "strategy" to find the 
> scenario problematic.
> 
> I guess people need to understand what ranking candidates in general or ranking 
> them above the last place means, and that such an act is supposed to mean 
> something when they vote, if they have an opinion on the Plurality criterion (or 
> on examples that demonstrate the impact of the Plurality criterion). Or do you 
> mean that the Plurality criterion example would be presented and explained to 
> the public, but assuming that they don't understand what ranking or not 
> ranking some candidate means?

Plurality is just a description that is convenient for discussion on the
EM list. "Ranking above last place" isn't a concept that exists (until 
someone feels it would aid their position to bring it up).

It just takes someone (could be an IRV advocate) to say this many voters 
ranked this candidate first and this candidate second, and didn't rank 
anyone else, etc. If this, without bringing up any criteria, doesn't 
raise an awful lot of eyebrows, then I'm wrong about Plurality. But if 
it does raise eyebrows, then it is up to the pro-margins crowd to explain 
to the public that their mistake is that they believe in "implicit approval"
(without having ever heard of it) and that they should stop, because it
(you will say) encourages harmful strategy.

And I want note again that virtually every proposed method satisfies 
Plurality aside from margins and MMPO. So if Plurality is the cause of 
some harmful strategy, your offered alternative must be something really
fantastic.

>>  That's why I see it as such a show-stopper.
>>>  I wonder if the voters should be told about the Plurality criterion or 
> if that
>>>  should be hidden from them (to avoid them rankig only those candidates 
> that 
>>>  they approve / want to promote). In some startegies that information 
> may be 
>>>  useful to them. But losing information because of truncation (in an 
> election 
>>>  that has no meaningful strategy problems) is harmful.
>>
>>  Do you think that if you permit IRV voters to know that IRV satisfies
>>  Plurality, they will truncate more often (assuming the rules allow them 
>>  to)?
> 
> Depends on how different properties are presented and advertised. If Plurality 
> would be presented as an important feature of Condorcet methods, some people 
> might take that seriously and vote accordingly (e.g. rank only those candidates 
> that they approve). That could be relevant in IRV too, if someone would start 
> merketing IRV using the Plurality criterion.

I can't imagine that anyone would use Plurality to promote a method, 
since even FPP satisfies it. I can only see using it to oppose a method,
and even then it seems unnecessary to put a name to the problem.

> But in general I lean in the direction that in most cases (e.g. in Burlington) 
> people will use ranked methods in some quite sincere way and they do not worry 
> about the details, like IRV strategies or Plurality criterion.

Ok. In the context of margins' proposability and Plurality I don't 
actually think it matters how people would vote under it. (Though I'm sure
it would come up. Ahaha.)

> However, even without stategy and property discussions, some voters may be 
> tempted to truncate just because they get the idea (maybe from their traditional 
> voting methods) that marking some candidate on the ballot will give him some 
> "points". But that would be based on lack of understanding and not on 
> the properties on the method in question.

Right. And when you advocate margins you get the job of convincing 
everybody that they're wrong to think this way. (I do think they think 
this way, and I don't think anyone can change it.)

> I think the correct message to voters 
> in most ranked method based elections is to encourage them not to truncate but 
> rank all ralevant (good and less good) candidates sincerely.

I actually don't understand the meaning of this kind of statement. Who 
is in the position of sending messages to voters? I think the political 
players will tell their supporters whatever they think is most advantageous,
and no one will consult the EM list.

>>  The thought that Plurality itself (satisfaction of it, or failures of it) 
>>  can be exploited by voters is strange to me.
> 
> Pluraity criterion can at least play a role in some strategies. Sincere rankings 
> are 49:A, 48:B>C, 3:C>B. If the three C supporters truncate, Plurality 
> criterion says that (former Condorcet winner) B can not win any more. Plurality 
> criterion does not say that C must win, but if it does (as in some Condorcet 
> methods), then those three C>B voters have a working strategy.

Ok.
 
> Also the wording and intent of Plurality criterion may lead people to think that 
> by not ranking some candidates at all, they can decrease the chancs of those 
> candidates to win (never mind if the voters are rational or not).

Ok. Though again, I see no use in bringing up this criterion except to
oppose a method that doesn't satisfy it.

Kevin