The Toda-Yamamoto approach
Toda and Yamamoto (1995) have developed a simple procedure that involves testing for
Granger non-causality in level VARs irrespective of whether the variables are integrated,
cointegrated or not. For this purpose, a VAR is estimated not with its ‘true’ lag order k
but with lag order of (k+d), where d is the maximal potential order of integration of the
variables. Then, Granger causality is tested by performing hypothesis tests in the VAR
ignoring the additional lags k+1, …, k+d. Toda and Yamamoto proved that in such a case
linear and nonlinear restrictions can be tested using standard asymptotic theory. This
method, which like the ARDL technique avoids the low-power unit root and
cointegration pre-tests, has recently been applied in several causality studies.
Following Seabra and Flach (2005), the T-Y Granger no-causality test is implemented in
this study by estimating the following Causality VAR system :