ABSTRACT
The four or ®ve core propositions concerning trade gains are now ®rmly established. In their more general forms, however, they are accessible only to a small coterie of trade specialists. Indeed the welfare economics of international trade is often criticised as excessively complicated. Our chief purpose in writing the present paper, therefore, is to present the propositions in a uni®ed and digestible form. Unity and accessibility are achieved by recourse to elementary duality theory, especially that part of the theory which deals with the properties of revenue and expenditure functions.1 Indeed our second purpose in writing the paper is to illustrate the power of duality theory in the welfare economics of international trade.
