----------------- HES POSTING ----------------- 
I think Humberto is right to point to the different way efficiency is used 
in engineering. I don't think the crucial difference is the one he 
highlights, though. Engineers want optimality, too, but they want the 
maximum *physical* output from given inputs. Economists want the maximum 
*utility* output from the inputs. With this change, I don't see much 
difference. The First Welfare Theorem says that any reallocation of an 
input will reduce the output of utility. A reallocation may well reduce 
energy usage, or raise the  number of tons of GDP produced, or some such. 
We don't care!  Engineers ignore values. 
 
Kevin Quinn 
 
 
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