Urbanization is the occurrence of unequal growth in cities, and it is happening throughout the developing world. During this decade, developing country cities will need to accommodate 180,000 new urban dwellers each day – that is more than one million a week. It is estimated that there are currently 837 million slum dwellers in the developing world, with a majority being children. At the projected rate of growth the number of slum dwellers will increase to approximately 1.5 billion by 2020, resulting in the urbanization of the poor and the young. Some of this growth is from in-migration, but a substantial percentage of it is from population growth of residents already living in cities.