In the comparative-statical calculations of the simplest two-commodity barter theory of international trade, the outcomes invariably depend on the magnitude of the sum of the two import-demand elasticities, one relating to the country under study (the ‘home’ country) and the other to the rest of the world (collectively, the ‘foreign’ country); in particular, the response of a variable to a disturbance will be in one direction if the sum of elasticities is less than minus 1 and in the opposite direction if the sum is greater than minus 1. On the other hand, for some dynamic or ‘disequilibrium’ models of international trade it is a necessary and sufficient condition of local stability that the same sum of elasticities be less than minus 1. Let us define Δ as one plus the sum of the two elasticities of import demand. Then the so-called Marshall–Lerner condition requires that Δ be negative. Evidently the condition provides a link between the comparative-statics of international trade and some forms of trade dynamics. That such a link exists is, of course, the essence of Samuelson’s correspondence principle.
KeywordsCorrespondence principle International trade theory Marshall–Lerner condition Terms of trade Transfer problem
- Kemp, M.C. 1964. The pure theory of international trade and investment. Englewood Cliffs: Prentice-Hall.Google Scholar
- Lerner, A.P. 1944. The economics of control. New York: Macmillan.Google Scholar
- Marshall, A. 1879. The pure theory of foreign trade. Published privately. Reprinted with The pure theory of domestic values. London: London School of Economics and Political Science, 1949.Google Scholar
- Marshall, A. 1923. Money, credit and commerce. London: Macmillan.Google Scholar
- Samuelson, P.A. 1947. Foundations of economic analysis. Cambridge, MA: Harvard University Press.Google Scholar