Central banks have always been able to make waves in markets. But never have they had such far-reaching effects, nor so quickly. The world of bonds is being turned upside down as a result.

Monetary policy traditionally has involved adjusting a short-term rate of interest that can then, over time, affect the structure of long-term rates that are set by markets. But central banks' bond purchases and ultra-low interest rates mean that distortions are rife.