[EM] Condorcet question - why not bullet vote

[Juho]

On Jun 17, 2010, at 12:29 AM, Kevin Venzke wrote:

> Hi Peter,
>
> --- En date de : Mer 16.6.10, Peter Zbornik <pzbornik at gmail.com> a  
> écrit :
>> Thus: "If the three C voters will truncate then they will win  
>> instead of B
>> in winning votes based Condorcet methods."
>>
>> This is correct, if proportional completion is not used (see page 42
>> in http://m-schulze.webhop.net/schulze2.pdf)
>> If proportional completion is used (which I would recommend) then B  
>> wins.
>
> If you are using proportional completion (or "symmetric completion")  
> then
> you're not using winning votes, you're using margins.

The described algorithm seemed to make the completion in a "non- 
symmetric" way, leading to comparing the proportions of the A>B and  
B>A votes.

>
> Juho advocates MinMax(margins) which is why he posted this example

Not really because of the minmax part but to cover also margins in  
addition to winning votes.

>
> (Schulze is usually assumed to use winning votes), and also why he  
> didn't
> like it when I pointed out that clone independence and ISDA were the
> probable answers to your criteria question

That was on the minmax part. Minmax doesn't meet the Smith criterion  
and clone independence (in some extreme situations). Also in this case  
I wanted to cover also those methods in the discussion (in addition to  
the usual Smith+WV ones and criteria that those methods meet).

Kevin Venzke is usually more on the WV and Smith set line (right?).

When it comes to real life elections I tend to think that all common  
Condorcet methods are pretty similar, and because of that similarity  
all the vulnerabilities and dramatic looking criteria do not mean that  
much in real elections. They make wonderful tools for propaganda  
though since one can construct dramatic looking (often just  
theoretical, not real life like) examples and criteria. All reasonable  
elections methods and all Condorcet methods violate some criteria that  
one probably would like to keep. It may also be that the best method  
(whatever that is) is one that violates numerous criteria but only  
slightly each one of them (and in situations that do not usually occur  
in real elections, or in some situations where the good looking  
criteria actually should be violated for some other more important  
reason).

 From practical Condorcet promotion point of view I don't recommend  
diving too deep in the world of different Condorcet variants and  
criteria. All typical Condorcet methods are exceptionally good single- 
winner methods for competitive environments. Better to concentrate on  
the properties of the Condorcet methods in general and just mention  
that there are different variants with slightly different properties.

Btw, when it comes to different Condorcet methods and their  
differences (different results) in real life elections I expect the  
first differences to emerge in the margins vs. winning votes ((vs.  
other possible approaches)) front. The Smith set and cycle of four (or  
more) related differences are probably not as common. I assume  
reasonably sincere voters here. Also truncation may lead to missing  
the true Condorcet winner (but this is more difficult to measure since  
people truncated their votes and their true preferences were thus not  
recorded for analysis after the election).

Juho




>
> Kevin Venzke
>
>
>
>
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