FOR as long as most people can remember, food has been getting cheaper and farming has been in decline. In 1974-2005 food prices on world markets fell by three-quarters in real terms. Food today is so cheap that the West is battling gluttony even as it scrapes piles of half-eaten leftovers into the bin.

That is why this year's price rise has been so extraordinary. Since the spring, wheat prices have doubled and almost every crop under the sun—maize, milk, oilseeds, you name it—is at or near a peak in nominal terms.