ABSTRACT
The three main sources of urban population growth are net migration, natural increase and the administrative reclassification of urban areas, with the first two being of greatest importance. In general, the relative contribution of migration and natural increase to urban growth varies with level of urbanisation (see Chapter 4). At an early stage of development, when levels of urbanisation are low and rates of both urban and rural natural increase are moderately high, net migration generally contributes more to urban population growth than natural increase. At an intermediate stage of urbanisation, natural increase predominates. At a later stage, with a high level of urbanisation and low rate of natural increase, the balance reverts in favour of net migration. Although some Third World countries are now in the intermediate stage and many large cities are growing more from natural increase, migration remains a major factor in urban growth and, in view of the size of the rural reservoir of potential migrants, will continue to be so for the foreseeable future. In this chapter we identify the major motives underlying rural-urban migration in the Third World and examine the key structural determinants of migration flows. We consider the characteristics of migrant populations and the different types of migration strategies adopted. We then assess the differing policy responses to large-scale rural-urban migration, ranging from efforts at preventing flows via the imposition of migration controls to various means of accommodating the influx of population.
