CITIES grow in three directions: in by crowding, up into multi-story buildings, or out toward the periphery. Although cities everywhere lave developed ill each of these ways at various times, nowhere ill Europe do urban settlements sprawl as much as in the United States. Less than a quarter of the U.S. population lived in suburbia in 1950. Now well over half does. Why have most European cities remained compact compared to the hyperextended American metropolis?