Central bankers would surely say that Mario Draghi pulled out the monetary version of a man-portable recoil-free anti-tank rocket launcher. To the ordinary investor and trader, it was enough to know that the president of the European Central Bank has fired his bazooka.

Ahead of the March 10 meeting of the ECB, investors were confused. With a bewildering array of options facing policymakers in Frankfurt, it was hard even to be sure what would count as good news. Taking rates more negative? Hurts banks. Buying more bonds? Simply means the program of quantitative easing will run out of eligible securities earlier.