The recent mass upheavals in Tunisia, Egypt, Libya, Yemen, and Syria gave political scientists a cha

The recent mass upheavals in Tunisia, Egypt, Libya, Yemen, and Syria gave political scientists a chance to analyze revolutions in real time. They found some similarities. The old regimes had suffered from weak legitimacy for decades; people knuckled under to them but did not respect them. Most of their population was young, under 30, a  “demographic bulge” that had some education but few jobs. Corruption, always massive, got worse as the growing economies multiplied the need for government permits. New mass media—satellite television, the Internet, and the hand-held social media—spread worldwide. A possibly triggering factor was the global increase in food prices that hit poor countries especially hard. These five factors—we do not yet know which were the most important—could deepen our understanding of revolution.