There was a time when gold was money. In today's uncertain world, the yellow metal is back in fashion. Bullion prices rose to a record nominal high after the assassination of Benazir Bhutto in Pakistan added to nervousness about the world economy. Part of gold's allure is its traditional status as a safe haven. It is seen as a store of value when everything else seems risky. But the bigger drivers behind the rising spot price are a depreciating dollar and the prospect of negative US real interest rates.

A better way to think of gold may be as central bankers used to before America dropped the gold standard: not as a commodity, but as another currency. As long as the dollar stays weak, gold's bull run will last.