[EM] Juho reply, 22 Feb., 1548 GMT

[Juho]

On Feb 22, 2007, at 17:49 , Michael Ossipoff wrote:

> Juho replies:

> One thus needs to add one to the worst margins defeat of a  
> candidate to get the number of additional voters that the candidate  
> needs to become a Condorcet winner.

> I reply:

> So to find out what it would take to make A the CW, in general,  
> would be to add up how many pair-wise preference votes would have  
> to be changed, summed over all the voters, to make A the CW. That’s  
> Dodgson, or something very similar.

I used the needed number of friendly additional voters to measure the  
distance to being a Condorcet winner since that is a simple way to do  
the measurement. Changing existing votes would be a much more  
difficult task (since it is difficult to anticipate what kind of  
ballots the voters will cast).

> In general, looking at A’s worse pair-wise defeat isn’t enough.

Didn't get this. Was my formula (see above) wrong? Maybe an example  
would clarify where the difference between our thoughts is.

> Juho replies:
>
> I think the best way forward would be to give practical examples of  
> situations where the methods fail due to strategic voting.

> I reply:
>
> I’d be glad to. I’ve posted those examples many times since the EM  
> list began. I’ve posted them for every “generation” of EM  
> membership. I’ll post them again in a subsequent posting.

The subsequent posting looked identical to the one that I'm replying  
to now. I hope the old examples are real life ones, or mappable to  
real life.

> You know that, in countries that use Plurality strategy is rampant.  
> It’s discussed and recommended, virtually coerced, by the media. As  
> people find out about margins’ strategy needs, they’ll publicize  
> and recommend them.

That would be good input for the discussion. I mean if you are able  
to write general(?) rules for regular voters on how to vote  
strategically.

> Juho continues:
>
> Here's my example. It is in principle the same one I already used  
> but now presented as a bit more realistic scenario. We have three  
> candidates: D=Democrat, C=CentristRepublican,  
> R=RightWingRepublican. I don't have any small party candidates, and  
> that's maybe a deviation from realism, but let's do this simple  
> scenario first. Sincere votes: 21: D 21: DC 03: DR 03: CD 26: CR  
> 26: RC Many Democratic voters truncated since they were not  
> interested in the Republican party internal battle between R and C.  
> The R supporters note that they could vote RD and get R elected  
> (with winning votes). They spread the word among the R supporters  
> and press too to reach the required number of voters. 6 out of the  
> 26 R supporters follow the recommended strategy (=> 20: RC, 06:  
> RD). R wins (with winning votes).

> I reply:

> Notice that the only reason why the R can succeed at that is  
> because the C are helping R. As I said, the only way you can  
> succeed in stealing the election by offensive order-reversal is if  
> your victims are trying to help you.

> Offensive order-reversal isn’t a natural way of voting, and it  
> would require organization and public discussion. It would be  
> impossible to conceal it from its intended victims, who’d then be  
> unlikely to rank R.

> If the intend victims don’t try to help the perpetrators, helping  
> with their own victimization, the offensive order-reversal will  
> fail, and will result in an outcome worse for the reversers than  
> the CW.

These are kind of good news to me. One reason why I'm talking about  
public large scale elections is that then all major strategic  
intentions would probably be known by other voters already before the  
election. In the example I gave I'd expect the popularity of R to  
decrease. The voters that would change the way they vote would not  
necessarily be insincere or strategic but just voters that have  
sincerely changed their opinion about R (and her tactics) before the  
election. Many C supporters maybe would rank R last (sincerely). You  
see, I'm trying to get a conclusion this strategy (and others) would  
not be feasible in large public elections in the first place.

You had also several comments about the higher vulnerability of  
margins. Maybe I'll get the chance to comment when I get the  
examples. Replying to all the criteria and their properties in  
different situations is a too tedious and EM bandwidth consuming task  
to try. One or two good examples should demonstrate the worst  
vulnerabilities well enough.

I hope you noted that the example I gave was intended to point out a  
situation where winning votes are vulnerable to a strategy and  
margins are not.

Juho


		
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