[EM] Sincere methods

[Juho Laatu]

Hello James,


On Apr 3, 2005, at 01:35, James Green-Armytage wrote:

> Juho Laatu <juho at bluebottle.com> writes:
>> If someone is interested, I would be happy to see examples e.g. on how
>> the "SVM: MinMax (margins), PVM: MinMax (margins)" case (this one
>> should be an easy target) can be fooled in large public elections  
>> (with
>> no more exact information than some opinion polls on how voters are
>> going to vote).
>
> I think that my 3/14 post provides such an example, and furthermore  
> makes
> it clear that such examples will be easy to find in general.
> http://lists.electorama.com/pipermail/election-methods-electorama.com/ 
> 2005-March/015125.html
>
> my best,
> James


I'll write a short story explaining why I see the case of large public  
elections different from the case of individual strategic manipulation  
examples.

The example you used (in the 3/15 post) was:

	Ex. 1: Sincere preferences:
46: A>B>C
44: B>A>C
5: C>A>B
5: C>B>A
	Ex. 1: Pairwise comparisons:
A>B 51-49
A>C 90-10
B>C 90-10

And the B voters then voted strategically 44: B>C>A and as a result B  
won the election.

My arguments are based on probabilities and the public nature and large  
scale of the election.

Let's say that these elections are some presidential elections in USA  
after a Condorcet based method has been taken into use. Candidate A  
could be from the republican party. Candidate B would obviously be from  
the democratic party. Candidate C is obviously not some centric  
compromise candidate since A and B voters seem to hate him. Let's say  
that he is a professional wrestler. The numbers obviously represent  
percentages of the total number of voters. The numbers are based on  
some opinion poll that has been performed some time before the  
election.

The democratic party is thus planning to vote strategically. I'll give  
some estimates to involved probabilities.
- probability of democrats giving a secret recommendation to all its  
supporters to vote B>C>A => low
- probability of democrats giving a public recommendation to all its  
supporters to vote B>C>A => low
- in both cases: probability of comparable number of republicans and  
others applying some strategy => high
   (one can thus not trust that the outcome will be as planned)
- probability of sufficient number of democrats voting as they were  
told => low
   (B will not win if more than 3 out of the 44 will not implement the  
ordered strategy (3 means a tie => 2 or less to win))
- probability of considerable portion of democrats voting sincerely  
even though they were told to vote strategically => high
- probability of many voters not understanding the strategy  
recommendation right or at all => high
- probability somewhat different voting behaviour than anticipated  
based on the opinion polls => high
- probability of some democrats not voting at all or voting republicans  
because they didn't play dirty strategy tricks before the election but  
emphasized the need to vote sincerely => high
- probability of C getting elected after everybody applying various  
strategies => low but increases considerably if democrats can make  
people vote as told
- probability of democrats getting their candidate elected by  
convincing few republicans to vote B => much higher than with strategic  
voting
- probability of democrats getting their candidate elected by  
convincing few C supporters to vote B => much higher than with  
strategic voting
- probability of democrats getting their candidate elected by  
convincing few C supporters to vote C>B>A instead of C>A>B => much  
higher than with strategic voting
   (1 for a tie, 2 for a win)

Maybe there are also other reasons. Maybe some that give support to  
strategic voting(??). And maybe the probability estimates could be more  
accurate. But based on this story the probability of deciding to  
implement the strategy in general, and the probability of a successful  
outcome of this strategic voting case is in my opinion not very high.

What do you think the probability of a) democrats recommending their  
voters to use this strategy in these elections and b) probability of  
success of the strategy if implemented is?

My message is that although there exist strategic voting patterns that  
lead to unwanted results, one has to estimate also how serious those  
theoretical risks are in real life (in this case in large public  
elections).

If strategies are as difficult to implement and results as hard to  
achieve as in this story, maybe one could get good results by using  
some sincere voting method and telling voters that the voting method is  
well planned and made sincere to take their sincere votes into account  
in the best possible way. If one would in addition tell that using  
strategies most likely harms the voters' intentions rather than  
supports them and best voting scientists would confirm this, maybe  
people would be first of all happy with the new method and secondly  
also vote sincerely.

Best Regards,
Juho