----------------- 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 ------------ FOOTER TO HES POSTING ------------ For information, send the message "info HES" to [log in to unmask]