They have proved popular and valuable in many fields such as advertising, prediction, developing trading strategies, and so on. Indeed, as the economic historian Joel Mokyr provocatively wrote “… who needs causation as long as we have correlation?”17 Big Data, however intriguing, is no panacea. Such methods rely on often multi-dimensional correlations fitted (perhaps over-fitted!)
Today, by contrast, it is clear that the Fed and the ECB, which have both made substantial recourse to unconventional measures, though differing in scale and modalities, were simply pursuing their own statutory objectives, by providing stimulus when shortterm interest rates were at the zero lower bound or by restoring the viability of the monetary policy transmission mechanism.