import demand functions for productive inputs. The contention of this paper is that the formulation of import functions (outlined above), though valid for consumer goods imports, is not reliable when one deals with intermediate products, the demand for which is mainly “derived demand.” The traditional import demand functions, which use gross national product (GNP) or a component of it as an explanatory variable, implicitly assume either that the unit import requirements of all components of GNP are equal or that the unit import requirements of several components of GNP