There was, last week, a glimmer of hope in the world food crisis. Expecting a bumper harvest, Ukraine relaxed restrictions on exports. Overnight, global wheat prices fell by 10 percent. By contrast, traders in Bangkok quote rice prices around $1,000 a ton, up from $460 two months ago. Such is the volatility of today's markets. We do not know how high food prices might go, nor how far they could fall. But one thing is certain: We have gone from an era of plenty to one of scarcity. Experts agree that food prices are not likely to return to the levels the world had grown accustomed to any time soon. Consumers are grumbling even in the wealthy nations of Europe and the United States. But imagine the situation of those living on less than $1 a day - the "bottom billion," the poorest of the world's poor. Most live in Africa, and many might typically spend two-thirds of their income on food. In Liberia last week, I heard how people have stopped purchasing imported rice by the bag. Instead, they increasingly buy it by the cup, because that's all they can afford. It is worth remembering that Liberia's descent into chaos began in 1979 with food riots. In Ivory Coast, political leaders told me how they worry that the crisis could undermine efforts to build real democracy - at a time, after a decade's effort, when they are so close to success. In Burkina Faso, President Blaise Compaor