A few weeks ago I had the pleasure of dining with two former luminaries of American economic policy. Unsurprisingly, the issue of quantitative easing provoked heated debate – not so much over the question of whether QE had been a correct policy to implement (they both backed its introduction) but whether the Federal Reserve could ever find a smooth exit.

The argument was illuminating, since it split along two lines. One of the dinner guests – who I shall call “Mr O”, or Optimist – argued that it was entirely possible for the Fed to achieve a smooth exit from QE. After all, he declared, the Fed did not necessarily need to actively do anything to find that exit, such as sell securities; instead, it merely needed to stop buying anything more. For if it duly sat on its hands, the two trillion dollars worth of assets it has recently accumulated on its balance sheet would automatically roll off (ie come to maturity), enabling the Fed balance sheet to return to pre-crisis levels over the course of the next seven or eight years.

Or to use a memorable image, what the Fed is essentially now doing – in the eyes of Mr O – is akin to a pilot stealthily landing a plane: once it powers down the motors, gravity will take hold, putting the balance sheet on a steady downward glide path. “There will be plenty of time to adjust, and even it’s a bit bumpy sometimes, that can be handled,” Mr O insisted. After all, Ben Bernanke, Fed chairman, has already told everyone well ahead of time to start fastening their seat belts to avoid any element of surprise. Hence this week’s statements.