[EM] Arrow's Theorem.

Eric Gorr eric at ericgorr.net
Tue Jul 15 11:15:10 PDT 2003

At 10:57 AM -0700 7/15/03, Alex Small wrote:
>Eric Gorr said:
>>  It still seems to me that Approval does have preference ballots.
>>  They are simply binary preferences (either you like the option or you
>>  don't) from which an outcome (I assume this means winner) is uniquely
>>  determined.
>True.  If all voters actually had binary preferences, then we could say
>that Approval is a ranked method because it allows voters to fully express
>their relative preferences.
>However, because Approval does not allow for non-binary preferences, it
>does not allow voters to express their complete preferences and is hence
>not a ranked method in the strict sense.

What is the source of this statement? Where does Arrow state that a 
voting system must allow the voters to fully express there complete 
preferences without equal rankings? Can you quote something explicit 
from his book and provide a reference to that?

Would you agree that if we end up finding that equal ranking allowed 
that Approval is covered by Arrow's Theorem and that we could then 
show that it fails?

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