The Granger causality test is a useful device to determine whether the lags of a variable, say, xit contribute to the
better forecasting of yit when the lagged values of xit are introduced into the regression of yit on the lagged values of
yit. In the panel data context, Granger non-causality can be tested by making use of a finite order panel VAR model
in the following form, where a random variable can be expressed as a function of its own past values and past values
of other variables in the system: