Portfolio stock adjustment and the real exchange rate: The Dollar-Mark (DM) and Mark-Sterling

The advent of “freely floating” exchange rates in the 1970's coincided with the emergence of what is known as “monetary” or “asset” models of exchange rate behavior where exchange ratesmove to equilibrate demand for stocks of monies. The fundamental monetary model assumes purchasing power parity holds in the long-run, and therefore exchange rates are determined by the same factors that determine relative prices, to wit, money stocks, real incomes, and nominal interest rates. Though early proponents of the monetary view clearly emphasized its long-run nature, empirical testing has by and large neglected this caveat. Thus a model developed for long-run equilibrium exchange rates has instead been tested many times over on short-run equilibrium rates. The latter require a distinct model of their own. This paper develops a short-run equilibrium exchange rate model based on deviations of the short-run exchange rate from its long-run equilibrium. The model differs in that all variables are cast in real terms. It also differs in that the monetary and current account exchange rate versions are shown to be subsets of the more general wealth/portfolio framework used here. The present model considers, in addition to stocks of monies, stocks of foreign assets, and stocks of domestic wealth.