The trouble with the undead is that they are terribly stubborn about remaining among the living. This makes good zombie films. It is less profitable elsewhere.

This year’s commodities horror movie is iron ore. Demand in China for steel is not what it was. The ‘Li Keqiang’ index of (relatively) trustworthy economic indicators hit a post-financial crisis low last month. Yet it has coincided with big international producers opting to increase, not cut, supplies of iron ore.

This is a classic attritional strategy. Iron ore for delivery in January to the Chinese port of Dalian dropped below $80 a tonne on Monday. Thus miners who extract ore for $85 or $90 a tonne in west Africa or China itself are straddling economic life and death. In theory, they should stop digging.