A few only became important during colonialism when they served as administrative or trading centers for European powers. In either case, the rapid pace of urbanization only took off after the Second World War as the world economy became more global and as colonized lands gained their independence. Unfortunately, developing countries have limited resources to help new migrants to the cities. With the exception of some countries in East Asia, their economies and industries are not strongly developed, so that unemployment is high and many migrants live in poor conditions in shanty towns and slums. Urban problems are not confined to the developing world.
Cities everywhere have problems of homelessness, drugs, violence and unemployment.
Urban growth is not confined to the developing world either. For example, many cities in the south and southwest of the United States, such as Phoenix, are among the fastest growing cities in the world. Urbanization is a global phenomenon. It is hard to predict what shape cities will take in the future. However, there could be changes in the world before then.