[EM]Definite Majority Choice, AWP, AM

[Juho Laatu]

Hello Chris,

I have one generic comment on evaluation of different voting methods.

Examples that include both sincere votes and altered votes nicely 
demonstrate the possibilities of strategic voting, but when the voting 
method gets a pile of ballots to be counted, no knowledge of which 
votes are sincere is available. I'll modify one of the examples to show 
what I mean.

On Mar 24, 2005, at 18:11, Chris Benham wrote:

> The first is copied from a Sep.22,04 James G-A post.
>
> 3 candidates: Kerry, Dean, and Bush. 100 voters.
>     Sincere preferences
> 19: K>D>>B
> 5: K>>D>B
> 4: K>>B>D
> 18: D>K>>B
> 5: D>>K>B
> 1: D>>B>K
> 25: B>>K>D
> 23: B>>D>K
>     Kerry is a Condorcet winner.
>
>     Altered preferences
> 19: K>D>>B
> 5: K>>D>B
> 4: K>>B>D
> 18: D>K>>B
> 5: D>>K>B
> 1: D>>B>K
> 21: B>>K>D
> 23: B>>D>K
> 4: B>D>>K (these are sincerely B>>K>D)
>     There is a cycle now, K>B>D>K

The voting method sees only the altered votes. Although the sincere CW 
would be K, a voting method that elects K is not necessarily good. In 
this case votes "4: B>D>>K" were altered. But as well it could have 
been that those votes were sincere and for example votes "4: K>>B>D" 
were altered. Lets say that the sincere votes of those K supporters are 
"4: K>>D>B". If that was the case, then the sincere CW would have been 
D.

Since the voting method can not know which votes are sincere and which 
not, I guess it should behave as the votes given in the election were 
the sincere votes. I can't find any good examples where the voting 
method would be able to identify some votes as insincere. Maybe in the 
case that all ballots that have X in the first place are identical one 
could guess that X supporters have agreed some strategy. But of course 
that could as well be their sincere uniform opinion.

So, it looks to me that in the example above the voting methods should 
behave as if there was a sincere cycle and not favour K any more than 
the others.

The best voting methods or voting organizers can do in this situation 
is to try to discourage strategic voting.

Best Regards,
Juho


((P.S. One possible deviation to this main rule is a voting method that 
is known to require some certain strategy from the voters (to give the 
best results). In this case one could assume in the result counting 
process of the voting method that all voters have voted according to 
this known strategy and results should therefore be calculated using 
this assumption. In this case the voting method of course could give 
unwanted results if all or majority of voters voted sincerely. Maybe 
one should redefine sincerity in this case => sincere votes are those 
that follow the recommended/expected voting practice and do that in the 
light of voter's sincere preferences.))

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