By the year 2008, the balance of the world's population will be living in citiies, a new study says. Most of this growth will take place in cities in developing coutries. These cities are growing up to five times as fast as cities in industrialized countries. The study, "The Dynamics of Global Urban Expansion," estimates that at the current growth rate, developing countries would have to build "a new city of 1 million people every week for the next 40 years."