It's pretty hard to establish causality, but there is one way I know of establishing that A did not cause B. In particular, if A came after B, then A did not ca

It's pretty hard to establish causality, but there is one way I know of establishing that A did not cause B. In particular, if A came after B, then A did not cause B. If sending signals back in time was possible, the hedge funds would have figured it out. If the demand shock happened first, then it wasn't caused by the supply shock.