Central banks play an important role in the course of national economies and the global economy. Their leaders are regularly feted or vilified, their policy pronouncements highly anticipated and routinely scrutinized. This is all the more so since the global financial crisis.

The past fifteen years in monetary policy is essentially the story of two mistakes and one triumph, argues Pierre L. Siklos, a professor of economics at Wilfrid Laurier University. One mistake was that central bankers underestimated the connection between finance and the real economy. The other was a failure to...