[EM] Arrow's Theorem.

[Alex Small]

Eric Gorr said:
> At 9:51 AM +0200 7/15/03, Markus Schulze wrote:
>>To be a preferential method, the method must be defined
>>on every possible set of orders of merit and must not
>>take more into consideration than just the orders of
>>merit.
>
> Would you agree that Plurality is covered by Arrow's Theorem?

Plurality does not _need_ preferential ballots, but the results of a
plurality election could be inferred from preferential ballots:  Count the
number of voters who ranked each candidate first.  If the results of an
election method can always be uniquely determined from preferential
ballots, then the method is equivalent to a preferential method, even if
some clever implementation avoids using preferential ballots.



Alex