Before revision:  We propose a new bootstrap test on unconditional and conditional Granger-causality  , as well as on their difference, to catch particularly prominent causality cycles . The null hypothesis is that each causality or causality difference is equal to the median across frequencies .
After revision:  We propose a new bootstrap test on unconditional and conditional Granger-causality , as well as on their difference, to catch particularly prominent causality cycles in relative terms. In particular, we consider a stochastic process derived applying independently the stationary bootstrap to the original series. Our null hypothesis is that each causality or causality difference is equal to the median across frequencies .