[EM] More FARCS problems

Chris Benham chrisjbenham at optusnet.com.au
Wed Mar 21 11:28:49 PDT 2007

Michael Ossipoff wrote:

>Chris said that people arrive at the polls intending to vote a certain way 
>in a rank method, and then find out that it's (say) Plurality or Approval. 
>Say it's Plurality. Their ranking that they arrive with would reasonably 
>have their favorite in 1st place (Yes, I know it's a no-no to speak of 
>Now, upon finding out that it's Plurality, they have strategic reason to 
>give their one vote to a lower choice compromise. But FARCS has them voting 
>consistent with their rankings, so that their 1st ranked candidate must be 
>the one they vote for in Plurality.

Yes. All the strategising (if any) is supposed to only happen between 
their sincere preferences and their
'intended ranking'.

>Or, if it's known to be a Plurality election, do they come to the polls 
>"intending" to vote a ranking that has their Plurality compromise at the top 
>of the ranking? 

>What about FBC? One must not get a better result by burying one's favorite. 
>But FARCS and votes-only doesn't allow speaking of favorites. So, what is it 
>then, does top-ranked replace favorite?
>But then, if the actual ballot has to be consistent with the ranking, the 
>top ranked candidate can't be buried.  So how could there be an FBC test?

Kevin's "Sincere Favourite" criterion seems fine to me. If  the voter's 
intended ranking is A=B>C and
this results in neither of  A or B winning, but some other intended 
ranking with one or both of A and B not
given top preference results in one of them winning, then SF is failed.

>       *Sincere Favorite*.
> /Suppose a subset of the ballots, all identical, rank every candidate 
> in S (where S contains at least two candidates) equal to each other, 
> and above every other candidate. Then, arbitrarily lowering some 
> candidate X from S on these ballots must not increase the probability 
> that the winner comes from S./
> A simpler way to word this would be: /You should never be able to help 
> your favorites by lowering one of them./

Chris Benham

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