In 19th century Bavaria rye prices correlated to property crime rates (see Correlations from weather to sociology). When food prices spiked in 2008 commentators were smart enough to mention this might have something to do with the riots across the 3rd world (see World’s poor are up in arms over food prices). The first half of 2011 has seen many riots in Africa and the Middle East and again it has been pointed out that at the same time we happen to see a food price spike on world markets (see “The Great Food Crisis of 2011” by Lester Brown and Middle East riots for food, interventions for oil?). Now a statistical study of the food price index and the riot frequencies is backing up the link.
Working with the hypothesis that “widespread unrest does not arise from long-standing political failings of the system, but rather from its sudden perceived failure to provide essential security to the population” Lagi and colleagues correlated food prices to riots. When marked on a graph of the UN food price index riots clearly cluster around price spikes. Most of the riot incidents that fall more or less outside a spike can be explained by additional extraordinary circumstances.
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| Food price index graphed from 2004-2011. Red lines mark riot incidents. The chance that the “Arab Spring” should have randomly coincided with the price peak is estimated to be less than six percent, even less if riots in each country are considered individually. |
The researchers do not conclude “high food prices cause riots”. What they say is expensive food could be one factor among others setting the stage for riots. When populations are hungry, it takes lesser trigger incidents to kick-start a riot.
“These observations are consistent with a hypothesis that high global food prices are a precipitating condition for social unrest.”
– Marco Lagi to Technology Review.
Two main causes for recent food price increases are named:
- Investor speculation in food prices (US market deregulated)
- Cultivation of biofuel crops on arable land (given subsidies)
The researchers are confident enough to predict “food riots occur above a threshold of the FAO price index of 210”. If prices are persistently higher than that they speculate global unrest will occur. (Although we’re currently above, don’t panic yet – it’s assumed to be a “bubble” created by investor speculation, soon to bust, driving prices below riot levels for some time.)
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| Same graph with inflation corrected price graph, trend lines and riot thresholds added. The trends (average price index estimates) are extrapolated to exceed the riot thresholds some time during 2012 or 2013. |
The authors sent a warning letter to the US government just four days before Mohamed Bouazizi set himself on fire in Tunisia.
Sources: Technology Review / The Cause Of Riots And The Price of Food and the original paper: 
Marco Lagi, Karla Z. Bertrand, Yaneer Bar-Yam (2011). The Food Crises and Political Instability in North Africa and the Middle East Physics and Society DOI: arxiv.org/abs/1108.2455
