The helicopters are metaphorical, of course. No one expects Japan to really shower its people with freshly minted bank notes but the effect of the radical monetary and fiscal stimulus policies it might announce next week will be the same.

The concept of helicopter money was dreamed up by the influential Chicago economist Milton Friedman in 1969 in a thought experiment to explore what the impact of a one-off massive increase in the money supply would have on an economy. The idea was explored by Mr Bernanke in 2002 when he argued that, in extremis, any government can always defeat deflation by simply printing money. His intervention earned him the uncomplimentary nickname “Helicopter Ben”.

The fact that many serious people are now considering the equivalent of a huge money drop is an indication of the growing realisation that the tools central banks have used since the financial crisis have missed their main goal of kick-starting economic recovery. Cutting interest rates to zero has been far less effective at stimulating growth than hoped; injecting money into the economy via the back door through quantitative easing has done no better. It is even arguable that QE has made things worse, widening an already yawning gap between rich and poor by stoking an asset price bubble and reminding people of the fragility of the global economy.