"Although the food price spikes of 2008 and 2011 did not reach the heights of the 1970s, price volatility—the amplitude of price movements over a particular period of time—has been at its highest level in the past 50 years. This volatility has affected wheat and maize prices in particular. For hard wheat, for example, there were an average of 27 days of excessive price volatility a year between January 2001 and December 2006 (according to a measure of price volatility recently developed at IFPRI1). From January 2007 to December 2011, the average number of days of excessive volatility more than doubled to 76 a year (Figure 2).2"
Food Prices: Riding the Roller Coaster, IFPRI, Global Food Policy Report 2011. http://www.ifpri.org/node/8436