A just-released U.N. report says that governments may have to intervene to burst the bubbles that have developed in the price of commodities like food staples and oil. The report blames a dysfunctional commodities market, and disputes the conventional economic wisdom that commodity prices went up because of demand:

"The changing role of commodity markets, which are turning into financial markets, has enormous repercussions for the economy," said one of the report's authors – Heiner Flassbeck, a director at the UN conference on trade and development (Unctad).

"The possibility of allowing governments' direct intervention in the physical and financial markets needs to be considered," the study concluded.

Investors are encouraged to behave like a herd, says the report, with few incentives to arbitrage or bet against the tide of rising prices. Without checks and balances in the system, investors create price bubbles that put many basic foodstuffs out of the reach of millions in the developing world.

[...] In April, the World Development Movement blamed Barclays Capital, the investment banking arm of the high street bank, for driving up prices. BarCap is the UK's biggest player in food commodity trading, and one of the top three banking players along with Goldman Sachs and Morgan Stanley. BarCap has pioneered the creation of derivatives that allow pension funds and other investors traditionally barred from commodities exchanges to bet on food prices. Nearly $270bn is invested in derivatives that follow commodity prices, up from $90bn in 2005, according to Unctad.

A separate report by the UN special rapporteur on the right to food, Olivier De Schutter, argued that the appetite for investments in commodities was even higher. He found that commodity index funds rose from $13bn (£7.9bn) in 2003 to $317bn by 2008. While there are no definitive figures on how those index funds break down, one estimate suggested their holdings in agricultural commodity markets rose from about $3bn to more than $55bn over that period.

Using these new derivative products, pension funds, especially in the US, have invested large slices of their overall portfolio in commodities as it has become more difficult to generate above average returns from more traditional sources of income, such as stock and bond markets.