[EM] Condorcet strategies (was: strategy-free Condorcet method after all!)

[Juho]

On Nov 24, 2009, at 12:00 AM, robert bristow-johnson wrote:

>
>> robert bristow-johnson wrote:
> ...
>>> i dunno how to, other than take the raw ballot data of some  
>>> existing IRV
>>> elections, but i would like to see how many of these municipal IRV
>>> elections, that if the ballots were tabulated according to Condorcet
>>> rules, that a cycle would occur.
>
> Kristofer Munsterhjelm wrote:
> ...
>> I haven't run the data through my simulator yet, but it seems  
>> cycles are
>> rare.
>
> i have to confess that i am less worked up about what pathologies  
> would result from a Condorcet cycle than i am about what pathologies  
> result from FPTP or IRV (or Borda or whoever) failing to elect the  
> Condorcet winner whether such exists.  we know the latter actually  
> happens in governmental elections.  i still have my doubts to any  
> significant prevalence of the former.
>
> on the rare occasion a cycle ever happens, probably Tideman Ranked- 
> Pairs would be the best compromise between a fairer Schulze beatpath  
> and some method that has sufficient "lucidity" that voters can  
> understand it and have confidence that no "funny business" is going  
> on.  but whether it's beatpath or ranked-pairs or IRV rules as the  
> method that resolves a cycle,  at least in this very rare occasion,  
> it's picking a non-Condorcet winner meaningfully, even if there are  
> conceptual ways to turn tactical with it.  but then, how profitable  
> is it to vote tactically when there is little probability to the  
> conditions that would serve such tactical voting?
>
> if it were one of those Condorcet methods and if there is little  
> likelihood of a cycle happening and if a savvy voter knows that, how  
> does it benefit his/her political interests to do anything other  
> than vote for their fav as their first choice and cover their ass  
> with a tolerable 2nd choice?  how are they ever (assuming no cycle)  
> hurting their favorite or helping any unranked candidates (tied for  
> last place, in this voter's esteem) beat the 2nd choice?  i really  
> find it hard to see the tactical interests as differing from the  
> sincere political interests.

Note that one very characteristic vulnerability of Condorcet methods  
is burying in such a situation where a sincere Condorcet winner exists  
but some voters create an artificial cycle by voting strategically.

There is one example in Wikipedia (http://en.wikipedia.org/wiki/Condorcet_method#Potential_for_tactical_voting 
). (This example for some reason talks a lot about the Schulze method  
although this example applies to most typical Condorcet methods.)

It is however true that in large public elections with voters that  
make independent decisions and can not be fully controlled by some  
central entity (like a party) or by themselves and have only  
incomplete and changing poll information available this type of  
vulnerability might not cause any problems. Sincere voting could thus  
be the main rule in Condorcet elections despite of these  
vulnerabilities.

Juho


>
> r b-j
>
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