Clive W.J. Granger has summarized his personal viewpoint on testing for cau
sality in numerous articles over the past 30 years and has outlined what he
considers to be a useful operational version of his original definition of
Granger causality, which he notes is partially alluded to in the Ph.D. dis
sertation of Norbert Wiener. This operational version of Granger causality
is based on a comparison of the one-step-ahead predictive ability of compet
ing models. However. Granger concludes his discussion by noting that it is
common practice to test for Granger causality using in-sample F-tests. The
practice of using in-sample type Granger causality tests continues to be pr
evalent. In this paper we develop simple (nonlinear) out-of-sample predicti
ve ability tests of the Granger non-causality null hypothesis, In addition,
Monte Carlo experiments are used to investigate the finite sample properit
es of the test. An empirical illustration shows that the choice of in-sampl
e versus out-of-sample Granger causality tests can crucially affect the con
clusions about the predictive content of money for output.