This paper tests the fundamental implication of classical stochastic macroeconomic models à la Sargent-Lucas, namely, that conditional means of real variables are invariant with respect to monetary and fiscal policy. Using a multiple-equations technique to examine U.S. data from 1952:II to 1972:III, the classical hypothesis (which includes the natural-rate hypothesis) is rejected. While such evidence does not completely rule out the possibility of classical behavior by the economy, it provides some reassurance for those predisposed toward policy activism.

This paper tests the fundamental implication of classical stochastic macroeconomic models à la Sargent-Lucas, namely, that conditional means of real variables are invariant with respect to monetary and fiscal policy. Using a multiple-equations technique to examine U.S. data from 1952:II to 1972:III, the classical hypothesis (which includes the natural-rate hypothesis) is rejected. While such evidence does not completely rule out the possibility of classical behavior by the economy, it provides some reassurance for those predisposed toward policy activism.