Cotton does not receive much attention, probably because nobody 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 good. 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 cotton prices have been rising steadily for 18 months, after four years of consumption exceeding production, according to the US Department of Agriculture. The USDA predicts 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 (which was less dramatic for cotton than for other crops) cotton prices spent most of the past decade bumping around the levels of the 1980s. Soya beans, meanwhile, are about 50 per cent higher, and easier to grow to boot.

But farmers may be responding to higher cotton prices. The USDA says US acreage has increased by 20 per cent this year. Because India has curbed exports and Pakistan is swamped, American cotton farmers will likely rake it in this year. But the extra supply comes just as the global recovery is weakening and with a dispute on the legality of US subsidies still unresolved. Farmers (and cotton bulls) should make hay – or cotton – while the sun shines.