[EM] Single-winner method with strong winners (was: Poll for favorite single winner voting system with OpaVote)

[Juho Laatu]

On 17.10.2011, at 1.44, Kevin Venzke wrote:

> Hi Juho,
>  
> Sorry in advance if I didn't read your message carefully enough, but I think I probably
> did:


For a skilled reader like you those two rows below that define the method should be enough. So I guess you know what the method will do.


> --- En date de : Dim 16.10.11, Juho Laatu <juho4880 at yahoo.co.uk> a écrit :
> 
> Use a Condorcet method to elect the winner among the most approved candidate pair and those who are at least as approved as the less approved of those two.
> - a pair of candidates is approved by a voter if she approves at least one of those candidates
> 
> This method is summable. One should sum up information about pairwise comparisons, pair approvals and individual approvals.
> 
> 20: A1 > A2 >>
> 15: A2 > A1 >>
> 33: B >> C
> 32: C >> B
> 
> In this example we have three major parties, A, B and C. Or alternatively we have four parties. In that case parties A1 and A2 are ideologically close to each others.
> 
> This method elects B since pair A1, B (or A2, B) is the most approved pair (approved by 68 voters), A2 is more approved than B, and B beats both A1 and A2 in pairwise comparison.
> 
>  
>  
> 
> Use of approvals typically requires a (sincere) strategy. In this method the voters should try to impact on which two candidates will be at least as approved as the most approved pair of candidates. That means that it would make sense to approve at least one candidate with reasonable chances to be among the most approved candidates (and not to approve too many of the candidates).
> 
> Does this method work well enough? Are this kind of methods useful methods in general?
>  
>  
>  
> I think that your method is similar to my single contest method. I believe you determine
> the critical pair of candidates in exactly the same way. However, while my method just
> has an instant runoff between those two candidates, you are possibly letting in some
> other candidates.

That is essential. Those "additional" candidates and extra round with some Condorcet method (= a good single winner method) are needed to make it work in the intended way (= according to the requirements in the requirements section).


> I don't think there is a big problem on paper... It's quite likely that I tested in my sim
> some methods very similar to your proposal, and didn't report on them just because I
> found them to be .


What would you expect to be the problems in this category of methods? Why are they less than the best?

Note also that the target of the method is somewhat different that the regular requirements for single winner methods (i.e. elect the strongest, not the compromise candidate). It is planned for a "few-party system" that should be an improved version of a plurality based "two-party system". But I guess strategic vulnerabilities should be treated pretty much the same way as with other methods.


> What I found to be of interest, of course, is that very little strategy remained on the
> ranking side of the method, since its main purpose was to resolve a two-way race.
> Your method will compromise on that a bit...


What do you mean with a two-way race? And what is the compromise?

The idea is to pick the winner among those candidates that can be considered to be at least equal in strength with "what single candidates of traditional two leading parties would be". Those candidates were picked by comparing their strength (= their level of approval) to the strength of the members of the most liked "proportional" pair.


> Do you have majority favorite covered...?


What do you mean with this?


One more characterization for all the readers. The proposed method is supposed to work pretty much as plurality does today with single-member districts. But it allows also third parties to run without becoming spoilers. And in a related manner it allows also multiple very similar parties to run, or one party to have multiple candidates without them becoming spoilers. And at the same time the method tries to eliminate the problems that may occur if one directly replaces plurality with Condorcet. I.e. the method aims at electing candidates with lots of strong (=approved) support, and avoids electing e.g. candidates that would be good compromise candidates but not approved by many (= one definition of a "weal candidate" that includes also "weak Condorcet winners").

Juho


>  
> Kevin
> ----
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