Confession time: a world where money is lent for several years to the governments of Japan, Germany and Switzerland at a negative interest rate is hard to comprehend.

Rationalised, yes. The ongoing experiment in stimulus measures, to charge banks for deposits held at some central banks, has made it expensive to hold cash. Some banks, pension funds and insurers must buy safe government debt irrespective of the price. Others may think prices can go higher, yields even lower.

Negative rates were also once an interesting thought experiment along the lines of the Chiemgauer, a local German currency invented in 2003 by an economics teacher, which loses 2 per cent of its value every three months. A strong incentive to spend today, rather than save for tomorrow.