For the first time since 1980, the price of gold hit $600 a troy ounce this week. It has more than doubled in five years. Crude oil is up more than sixfold since 1999. Copper prices, which usually attract little attention, are breaking records and have tripled since 2000. Pimco, the world's largest manager of fixed-income securities, has a commodities fund that rose 50 per cent in two years between the end of 2003 and the end of 2005. Countries we seldom hear about, such as Nigeria or Peru, are making front-page headlines.

What is going on? Economic trends of this nature always attract attention, rumours and frights. Part of the explanation for the commodities boom is obvious, part is mystery. The consequences are the most interesting feature of the story.