Injustice is tough to quantify.
There are no formulas for the human cost of living in an autocracy, the dilution of human rights, the grind of enduring unemployment and instability.
An increase in the cost of food, though, is instantly measurable. Among people struggling with feelings of insecurity and exploitation, it also becomes a manifestation of life's unfairness - and a cause for action.
"It's the sense of injustice rather than price volatility that ultimately causes the rioting," said Evan Fraser, co-author of the book Empires of Food: Feast, Famine and the Rise and Fall of Civilizations.
All over the world, commodity price spikes have been driving people into the streets. High costs of staple foods, coupled with fears over shortages, have been cited for galvanizing masses in Tunisia, an act which spiraled into a revolution. Protests spread to Algeria, Morocco, Yemen and most notably to Egypt, the world's largest importer of wheat.
For months, Hosni Mubarak's government has been stockpiling wheat in hopes that a stable food supply would prevent civil unrest from bubbling over uncontrollably. The plan didn't work. A frustrated population took to the streets and now there are worries that global food prices, at record highs will further fan the discontent.
"The perception of food profiteering hits people on a very visceral level. People are so powerless to do anything about them, and people have to have their daily bread," Prof. Fraser said. "In a volatile situation where you've got all these grievances anyways, history demonstrates [food]is often the spark that hits the tinderbox."
Although they're triggered by price spikes, food riots are not typically about food at all, he argues. While it's true that people are propelled into the streets by having to pay higher prices for onions (India), stomach five-fold increases for chilies (Indonesia) and light buildings on fire over hikes for milk, sugar and flour (Algeria) - not all price hikes have set off riots throughout history. Underpinning the recent spate is a unique psychology - a complicated tangle of fear, insecurity, desperation and anger.
That Egypt's leaders know this is evidenced by their hoarding wheat last fall. A Russian ban on wheat exports after a disastrous summer growing season triggered cross-country lineups for bread, or aish, which translates to the word "life." Shortages triggered social upheaval there before. In 1977, the Egyptian Bread Riots broke out after a national subsidy program was axed. Deadly protests ensued. Another round of protests broke out in 2008 when food prices soared even though there was no real shortage.
Despite the fact that 40 per cent of Egypt's 80 million residents live in poverty, high food prices should not translate into the widespread hunger it might trigger in other vulnerable nations. Egypt has a subsidy program that, when working correctly, insulates its poorest from inflationary food prices.
Still, the injustice that higher food prices represent is a powerful motivator of protests. Often, poor people suffer in silence; those who are less hungry, but nonetheless incensed, take to the streets.
"The people who are attentive and organized and politically mobilized for this kind of activity are not usually chronically undernourished They're hurt by high prices not in their stomachs, but in their pocketbooks," said Robert Paarlberg, a food security expert at Wellesley College and Harvard University.
"People in Egypt are not hungry. In Cairo, the average calorie intake is 4,000 calories per day," he said. "Egypt has more serious health problems linked to … excessive nutrient intake than inadequate," he said.
The phenomenon is not unique to Egypt. Deadly food-related protests broke out last fall in Mozambique's capital, Maputo, over high wheat prices. However, wheat makes up less than 10 per cent of the average calorie intake there. Wheat prices had only a slight impact on daily diets, but people were nonetheless moved to riot over them in the streets.
The political instability caused by this type of rioting - and the puzzle of figuring out how to stop it - has been a top priority for many global food policy experts since price spikes in 2008 set off violence in Haiti, Pakistan, Egypt and elsewhere. Multiple factors play on the volatility of commodity markets. Those range from climate change to improved diets in developing economies of China and India and the impact of seemingly unrelated hedge funds which buy up commodities to diversify their portfolios.
The interplay of all that creates price swings that are increasingly difficult to predict. Thus, creating policies to insulate vulnerable nations from the impact of those price swings is equally challenging.
Acting on their own, some nations have taken measures to try to insulate themselves. Russia, for example, enacted an export ban on wheat last year after drought decimated much of its summer crop. Economists harshly criticized the move. Most advocate for less intervention in world markets - fewer subsidies and trade agreements that affect prices - rather than more. The idea behind this is that markets, allowed to function naturally, will ultimately stabilize themselves.
But hungry people - or people who fear they'll go hungry - have fewer patience than theoretical economists. Governments are well aware of this; many states have been more apt to intervene in markets to keep prices down. Their rationale is that a satiated population will have less reason to protest.
Most economists would scoff at supporting this. But Prof. Fraser said the concept of using protectionist policies in the short term (allowing small stockpiles of commodities, subsidizing food at the local level to insulate people from global price swings) could mollify disgruntled populations. The result? Stability and security.
"If you want to avert a crisis this week, you're going to have to act in some way that acknowledges the psychological element of these things," Prof. Fraser warned. "The disruption - the rioting, the burning, the looting and the pillaging - is more disruptive than the price rises themselves."