The movement of people from the countryside to cities is a significant feature of the recent development process of many Asian, African, and Latin American countries. Insofar as development is measured by production of goods and services (GDP), there is a high correlation between level of development and the degree of urbanization. The urban population makes up 78% of the total population among the world's industrial, market-economy countries, 34% in the lower-middle-income countries, and 21 % in the low-income counties (World Bank, 1984).
Most people in the regions that comprise the Third World still live in rural areas. But the proportion living in urban areas has grown from 20% in 1960 to 27% in 1980. Urbanization accelerated in many countries in the 1970s as greater numbers of people migrated to cities seeking work. In many of the poorest countries (mostly in African), the growth rate of the urban population average more than 6% per year during the 1970s. Together, the developing countries now contain more than 250 cities with population over 500,000.
Urbanization brings with it changes in the ways resources are collected, distributed, and used. In rural areas, people are more directly involved in these activities, whether it be growing food, gathering firewood, or hauling water. In cities, there is greater dependence on a supply network to meet these needs. As the cities of the developing countries rapidly grow, there is increasing pressure upon these networks, and in many cases, concern about whether they will be able to cope with the growing demand (Meier, et al., 1981). Understanding in the nature of urban resource consumption, and in particular, the changes that take place as a country's population becomes more urban, is an important element in planning urban supply networks that will be able to accommodate future demands.