Quantitative easing is here with a vengeance. Japan, the UK and Switzerland are doing it. Now the US is too, with Canada and Sweden expected to follow next. There are important differences, though, between the monetary policy of the US and the rest. Not all QE is equal.

Ostensibly, all central banks using QE are targeting the quantity of money in the system – hence “quantitative easing”. What they really seem to want to do, however, is to influence other key variables, such as bond yields and, in some cases, the exchange rate. Both fall sharply when QE is announced.

Buying government and corporate bonds with money created for the purpose will, it is hoped, reduce all borrowing costs. Meanwhile, a lower exchange rate can help the economy as a whole. It boosts the competitiveness of exporters at a time of falling world demand. It can also help loosen monetary policy generally, the reason the Swiss central bank gave when it began QE.