In the first half of 2008, commodity prices moved up quickly – and plummeted just as fast in the second half of the year. There may well have been speculative behavior that contributed to the rapid swing.
但2011这场上涨根源于比以往更加广泛的商品供应不足。在2008年上半年，商品价格迅速上升——在下半年又以同样的速度下跌。而且显然有投机行为促成了这样的迅速波动。