Marco Lagi, Karla Z. Bertrand and Yaneer Bar-Yam of the New England Complex Systems Institute have a working paper up about "The Food Crises and Political Instability in North Africa and the Middle East." This figure tells the heart of the story. The black line shows the two recent spikes in global food prices, one in 2008 and one in 2011. The vertical red lines show the dates of various food riots and/or civil disruptions, with the number of deaths shown in parentheses.Of course, food prices aren't the only factor in causing such disruptions, but the fact that such riots and disruptions essentially vanished in 2009 and 2010, in the time period between the two price spikes, is nonetheless striking.
Thanks to the Instapundit website for the pointer to this study. I've posted a couple of times recently on the subject of the global spike in food prices in 2008 and again in 2011 (see here and here). I've also posted a couple of times in the last few months on how unemployment and poor economic conditions have contributed to political unrest in the Middle East (for example, here and here).