IFE. Theory that the currency of a nation with a comparatively higher interest rate will depreciate in value in comparison to the currency of a nation with a comparatively lower interest rate. It further implies that the extent of depreciation will be equal to the difference in interest rates in those two nations. It is based on the observation that the level of real interest rate in an economy is closely linked to the level of local inflation rate and is independent of a government's monetary policies. Thus, in general, the higher the inflation rate, the lower the value of currency. Named after its proposer, the U.S. economist Irving Fisher (1867-1947).