The process of urbanization is related to the process of development. Urbanization is measured by the urban population rate or urban population growth rate, and it can be argued that urbanization follows the trajectory of economic development. When East Asia was just beginning to urbanize, Japan, the most industrially developed country, had the highest proportion of urban population, but Korea's urban population grew faster. OECD countries have a higher proportion of urban populations, but population growth has slowed. Urbanization in Africa and Asia including Vietnam, where most of the world's population is located, is also a huge opportunity for sustainability, if the right policies are put in place.