Virtually any commodity can move around the world to satisfy demand but human beings have far less freedom. Many would-be migrants are forced to risk life and limb travelling illegally yet most rich countries are short of workers, have shrinking populations and need more immigrants. This is a timely guide to a major issue that is never far from the political headlines. Author Peter Stalker is a former co-editor of the New Internationalist who now works as a consultant to a number of UN agencies.