But, unlike most of the reams of macroeconomic information with which we are bombarded every day, central bankers’ speeches and opinions have relatively foreseeable effects, especially when the bank’s chair, president, or governor speaks, or other officials speak in concert. And, with trillions of dollars swirling around global financial markets, this predictability creates a fat target, with investors willing to make massive bets when they are pretty sure they are right, even if the profit per dollar is small.