[EM] IRV vs Plurality (or is it about Range? maybe it should be about Condorcet.)

[Juho]

On Jan 28, 2010, at 10:33 PM, robert bristow-johnson wrote:

> On Jan 28, 2010, at 3:12 PM, Juho wrote:
>
>> On Jan 28, 2010, at 8:20 PM, robert bristow-johnson wrote:
> ...
>>> no, i think that if i can think up a negative number with greater  
>>> magnitude than anyone else, i should be able to single-handedly  
>>> scuttle a popular candidate.
>>
>> Ok, you seem to think that one can not get rid of strategic voting  
>> in typical (political I guess) elections.
>
> i think there are ways of not encouraging strategic voting by not  
> punishing sincere voting.  i'll defer to Arrow and the common wisdom  
> here that ultimately no system completely ditches strategic voting  
> under all conceivable conditions.

Yes. Arrow's statements of course leaves space for methods that are  
strategy free enough to work in practice as if they were strategy  
free. (I should btw have talked only about not getting rid of the  
interest of voters to vote strategically.)


>>> this is the strategy problem of Olympic judges (say of figure  
>>> skating or gymnastics or something with 8 judges holding up cards  
>>> rating the performance).  there is a problem with adding sincere  
>>> ratings to insincere and exaggerated ratings.  *especially* with a  
>>> secret ballot where no one needs to own up to and justify their  
>>> exaggerated rating.
>>
>> In ski jumping the practice is that the highest and lowest score  
>> will not be included in the sum of votes. This approach is  
>> somewhere between mean and median. Maybe it has some benefits of  
>> both. Judges come from different major ski jumping countries so  
>> often one of the judges has a temptation to vote strategically.  
>> Votes are public, so a strong bias will be visible.
>
> and, again, my point is that with my secret ballot, and my suspicion  
> that political opponents may well be voting with exaggerated  
> ratings, that *i* would feel pressured to exaggerate *my*  
> preferences and that i might expect *any* savvy voter to do the  
> same.  then, if everyone does that, the continuous gradation of  
> Range loses its meaning.

Yes, strategic voting escalates since it doesn't make sense to anyone  
to let the strategists decide and let the sincere votes to be ignored.


>>> with the exception of the strategy called "compromising".  that  
>>> happens quite a bit when there are more than two candidates and  
>>> there are at least two candidates that go into the election nearly  
>>> evenly matched in pre-election polls.
>>>
>>> it's amazing that anyone touts Range as the most strategy free.   
>>> the more handles one finds on a control device (think of the  
>>> ballot as such) or the more positions one can set the knobs to,  
>>> the more one has to strategize on how to control it to one's intent.
>>
>> The basic Range strategy is unfortunately present in almost all  
>> elections,
>
> i don't see how it would be with a simple ranked-order ballot.   
> especially, if decided by Condorcet, you cannot exaggerate your  
> rankings.  if you like A better than anyone and you like B better  
> than C, then there is nothing to be gained by any other ranking than  
> A>B>C.  if you really hate C, you can rank a bunch of other  
> candidates you don't care about between B and C.  but it doesn't  
> change how the election would work between the candidates A, B, and C.

Yes, the main rule in Condorcet is that sincere voting is enough.  
Condorcet has also strategic vulnerabilities but in most environments  
one can expect those problems to be so marginal that sincere voting  
will be dominant and is the most practical "strategy" for all voters.

Juho