Most studies of the effects of subsidies or recipient behavior accept the nominal legal provisions of a grant as defining the actual effective resource constraint faced by the receiver. This paper argues that to the contrary the true effect of a subsidy on the receiver's resource constraint can not be read from nominal administrative requirements. Therefore, an indirect statistical method is required to discover the shape of the post subsidy budget line. This paper develops such a method, which is then applied to U.S. local government expenditure decisions on education for the period 1964–71.