Stock markets have had a bad week. Once oil prices began to fall from the peak reached in mid-July, share prices stabilised and in some markets even rallied. But now a worrying insight has, rather belatedly, taken hold: the weakness of the global economy has caused the fall in commodity prices. That can hardly be good news for equities.

This economic weakness is partly the delayed result of past rises in the cost of food and energy, which are curtailing consumer spending. If one adds in rising unemployment, the collapsing value of houses and now falling shares in high-income countries, it is hardly surprising that consumers are feeling gloomy. This is reflected in slumping retail sales: a new car and the weekend abroad will have to wait.