Cotton does not receive much attention, probably because no one eats it or puts it in their cars. For a commodity, prices have not been very volatile, and anyway there are cheap substitutes for an already cheap product. Lately, though, some clothing retailers have threatened to increase prices, blaming the cost of cotton, which could soon reach a 15-year high.

Unlike wheat and barley, cotton is not just reacting to this summer’s crazy weather. True, large parts of Pakistan, the world’s fourth-largest cotton producer and second-largest importer, are under water. But prices have been rising steadily for 18 months, after four years of consumption exceeding production, according to the US Department of Agriculture. The USDA forecasts this year’s stockpiles will be only about 40 per cent of annual demand, the lowest level for 15 years.

The production problem has been centred in the US, the world’s biggest exporter (China is the biggest producer). Heavy government cotton subsidies notwithstanding, many American farmers switched from cotton to soya beans. Price was one factor: with the brief exception of the 2008 commodity bubble spike, cotton prices spent most of the past decade bumping around the levels of the 1980s. Soya is about 50 per cent higher, and easier to grow to boot.