[EM] IRV vs Plurality

[Juho]

On Jan 26, 2010, at 4:43 AM, Abd ul-Rahman Lomax wrote:

> At 07:22 PM 1/25/2010, Juho wrote:
>
>> There are many (working) uses for an approval cutoff in ranked
>> ballots. But on the other hand they may add complexity and confusion
>> and not add anything essential. => Careful consideration needed.
>
> Only a voting systems theorist who is not a parliamentarian or  
> familiar with the principles of parliamentary traditions, essential  
> in direct democracy, would think approval not relevant. Approval is  
> Yes/No on the series of possible choices. It's fundamental,  
> actually, and compromises with this are *never* made in direct  
> democracies, they are only made in the name of efficiency in large- 
> scale elections.

I referred only to approval cutoffs as additional components in  
existing methods.

>
>>> Bucklin does that, basically, by only considering approval votes,
>>> but it sets up a declining approval cutoff, typically in three
>>> batches, loosely named as Favorite, Preferred, and Approved. I've
>>> suggested that in a runoff voting situation, majority required,
>>> "Approved" has a very specific meaning: it means "I would prefer to
>>> see this candidate elected over holding a runoff election." Voters,
>>> then, by what candidates they choose to approve given their overall
>>> understanding of election possibilities, will sincerely vote this.
>>> It makes no sense not to.
>>
>> Bucklin is a bit simpler.
>
> Simpler than what? The proposed method? Sure.
>
>>> By definition, range methods put extra weight on first preferences,
>>> if the voter chooses to express the first preference exclusively, as
>>> does Bucklin, at least in the first round.
>>
>> Range is also designed to elect candidates with no core support, e.g.
>> one that gets 60% of the points from all voters while all others have
>> only limited amount of strong support and no support from the rest.
>> IRV puts always main weight on first preferences (among the remaining
>> candidates).
>
> Yes. However, "designed to elect candidates with no core support" is  
> an overstatement. It certainly is not designed for that, but it  
> allows it. It's pretty unlikely, eh?

Yes, but desirable if one wants to respect the basic philosophy of sum  
of ratings.

> The most common response to this claim when it comes from FairVote  
> is,"Really, even the candidate and her mother prefer someone else?"  
> And when there really is a problem with core support, it comes down  
> to, usually, center squeeze, and the compromise winner is, in fact,  
> quite strong in first preference votes, but merely ends up, in a  
> three-way race, in third place, and not by a large margin. Not at  
> all "no core support."
>
> Appeasing the "core support criterion" is a very bad idea, rewarding  
> partisan affiliation without sound reason for it; the only arguments  
> I've seen for it that carry any weight are arguments that core  
> support is necessary for good governance, which is not entirely  
> incorrect, but which doesn't counterbalance the danger of serious  
> social division. Remember that the Nazi Party in Germany had "core  
> support." Mmmm, did that help them govern? Sure it did! But "good  
> governance"? No, not at all, I certainly hope we will agree. Any  
> core support criterion pushes results away from true majority- 
> supported results toward domination by the largest faction. Which,  
> of course, then encourages a two-party system, at best.

There is no good definition of core support. It is quite possible that  
there are elections where core support or weight on first preferences  
is a desirable feature. But it is hard to discuss and judge as long as  
that feature is not well specified (I don't consider the operational  
definition as derived from how IRV works to be a proper definition).

Juho