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

[Juho Laatu]

On 25.6.2013, at 11.57, Kristofer Munsterhjelm wrote:

> On 06/25/2013 09:00 AM, Juho Laatu wrote:
>> On 25.6.2013, at 1.06, Kristofer Munsterhjelm wrote:
>> 
>>> Remember that criterion compliances are absolute. So a method may
>>> fail a criterion yet be perfectly acceptable in real elections.
>> 
>> I just want to support this viewpoint. It is not essential how many
>> criteria a mehod violates. It is more important how bad those
>> violations are, i.e. if the method likely have serious problems or
>> not. The best method might well be a method that violates multiple
>> criteria, but manages to spread the  (unavoidable) problems evenly so
>> that all of them stay insignificant.
> 
> In a sense, it's like certain kinds of mathematical tests. There are primality tests that return either "this number is definitely a prime" or "this number might be prime or might be composite". If you get the former result, you know you're dealing with a prime, but if you get the second, you don't know whether you're dealing with a prime or a composite number.
> 
> Criterion compliances are similar. If something passes IIA, you don't have to worry about candidates being added or removed as long as the voters don't alter their votes when the candidates are being added/removed. Whatever the dynamics might be on the nomination side, IIA secures the method. On the other hand, if something fails IIA, then you have the "might be" scenario. The method might fail IIA in blatant ways, or it might fail it where it doesn't really matter. You don't know.

Yes. Often you also know that although some method violates some criterion in practice it will (almost or completely certailnly) not cause any problems. We may also have a balance of benefits and problems where the benefits the problems so that e.g. trying some theoretically possible stratgy simply does not makes sense (= is more likely to cause damage than benefits). In this case there is no compliance but there is a strong understanding that there will be no problems. In the EM list discussions people often do not keep the difference of theoretical vulnerabilities and practical vulnerabilitis (in real life elections, maybe in some given political environment) clear enough.

> 
> In my case, I do like the certainty that criterion compliance provides, but sometimes, it just isn't available.
> 
> There is, though, one situation where criterion compliances go both ways. The method might produce a result that goes so completely against common sense that opponents can use it to argue against the method, even if that result itself only would appear very rarely. Perception does matter; and it's reasonable that it does, because sometimes the bizarre failure is symptomatic of a method that behaves strangely under pressure in general. That is not true all the time, though.
> 

It is good to handle both concerns. I like to discuss first about the properties of each method at abstract / technical / theoretical level, and then give also some consideration to how such methods would fit and could be marketed in some given political environments.

What I don't like is method and criteria names that have been chosen to be as good for positive or negative marketing as possible. In the theoretical discussions the ugly and pretty names should have no meaning (except to idetify a criterion or method).

Condorcet methods are an interesting example since in many cases their violations deal with situations where opinions are cyclical. In real elections sincere top level cycles are not very common, and artificially generated cycles (as a result of successfully implemented strategies) may also be difficult to generate and may easily lead to unwanted results from the strategists' point of view. The problem thus is that marginal violations (that voters actually need not worry about at all) will be marketed as major flaws that make it impossible to use the method in all real elections. Failing to meet FBC does not mean that voters are expected to "betray" or should always seriously consider "betraying" their favourite. Strategy "never betray your favourite" or "always vote sincerely" may lead to better results and may well be the best strategy for the voters (of all opinion groups) to follow.

One can compare the vulnerabilities of the election methods also to security systems. In that area one often says that a system is as strong as its weakest link. Also in election methods one could optimize the system based on how strong the weakest link is. That means (roughly) that we need not worry how many flaws the stronger links have as long as those links are still stronger than the weakest link (and if weakening a strong link allows us to make a weak link stronger).

In summary, I want to clearly separate discussion on the theoretical properties of the methods, on the practical properties of the methods (in real life elections), and on the marketability of the methods (to the politicians, media and general audience).

Juho