The US recovery from the subprime mortgage crisis of 2008 may seem stronger than that seen in other major economies. But given near-zero interest rates, it lacks lustre. Pundits are particularly concerned with the depressed level of employment.

Eschewing traditional monetary targets, the Federal Reserve has vowed to keep short-term interest rates near zero until the unemployment rate, currently at 7.8%, falls to less than 6.5% of the labour force. A laudable goal politically, no doubt; but the