The more gloomy possibility is that the hedge funds are right and that commodities are acting as a leading indicator of a global recession.

ECONOMIST: Making sense of the fall in commodity prices

Whereas big swings in oil prices usually reflect supply shocks, and precious metals are often seen as a safe haven in times of crisis, The Economist's commodity price index (which excludes oil and precious metals) has traditionally been a fairly good leading indicator of turning-points in global industrial output.

ECONOMIST: The prices of most raw materials have been surging