Ben Bernanke has sketched out a route to the exit, but does not intend to use it for a while. The chairman of the Federal Reserve released testimony yesterday that set out plans for removing the novel and extraordinary monetary props with which his central bank has shored up the sickly US economy during the financial crisis.

In September 2007, the Fed started to cut interest rates from 5.25 per cent. By the end of 2008, it neared zero. Still, the monetary authority went further, buying securities to press new money into circulation. By the end of March, when its asset-buying programme is due to finish, the Fed will have bought $300bn of Treasuries and $1,400bn of mortgage-linked assets.

This extreme loosening was – and is – justified: the Fed faced a credit crisis, a deep global recession and rising unemployment. But it will, at some point, be necessary to unwind these measures and disposing of such a portfolio without causing collapses in prices will be a slow process. So Mr Bernanke has explained other tricks he can use to soak up excess money.