High food prices are today a serious humanitarian concern. They are also a source of macroeconomic instability affecting budgets, trade balances and, of course, incomes almost everywhere in the world.

Global rice prices have increased more than 50 per cent so far this year and most other food prices are up sharply. As the global economy slows, the prices for all kinds of commodities are moving up - the opposite of what we would ordinarily expect. In part this reflects strong demand from emerging markets. But financial turmoil has also increased the attractiveness of commodities as an asset class.