US News and World Report: The troubles erupted early last year. First, there were the tortilla riots in Mexico City: 75,000 angry demonstrators, mostly poor, taking to the streets to protest the surging price of a food staple. Then in Italy, merchants from Milan began clamoring about the cost of pasta. By year’s end, protests had broken out in at least a dozen countries: in India over onions, in Indonesia over soybeans, and, last month, in the small African country of Burkina Faso, where hundreds of looters burned …