[EM] equilibria

[Steve Eppley]

James G-A wrote:
> Adam wrote:
>> James, this argument has been advanced before.  
>> Look up Nash Equilibria in the archives.
> 
> 	Okay, I did a quick search. 
-snip-
> Mike wrote:
>> As we on EM have been using the term for voting systems, 
>> a Nash equilibrium is an outcome, and the votes
>> configuration that caused it, that no set of voters 
>> can improve on for themselves by voting differently. 
-snip-

Mike's definition here is incorrect.  He gave the 
definition for a "group strategy equilibrium." 
Those equilibria are rarer than Nash equilibria, 
which merely require that no _individual_ voter 
can get an outcome she prefers more by changing 
her vote (holding all the other votes constant).
--Steve