Call it the rubber ball theory of economics. What goes down fast, springs back with equivalent velocity. Companies that have cut payrolls and slashed inventories are forced to rehire and restock rapidly as the downturn comes to an end. Such expenditures will get the economic flywheel humming again. This is not bad economic reasoning. But it’s a far better description of the volatile boom-and-bust cycle of the Victorian age or a modern emerging market than the behaviour of the pampered advanced economies of today.

The most distinguished exponent of the rapid recovery thesis is James Grant, the generally sceptical editor of Grant’s Interest Rate Observer. “The steeper the slump,” he writes, “the more and exaggerated the reaction to it, and the more volatile the snapback.”