The Dynamics of Two Demographic Models of Urbanization

This paper is the first of a series of three which attempt to shed some light on the urbanization phenomenon, using two alternative models of rural-urban population growth. One is a model recently proposed by Keyfitz (1978) in which migration is viewed as a net flow out of the rural region; the other is a continuous two-region version of the model of population growth and distribution developed by Rogers (1968), in which the gross migration flows out of both rural and urban regions are explicitly considered. This first paper examines and compares the dynamics of these alternative models on the basis of constant rates of natural increase and migration. It demonstrates the simplicity of their properties, especially in the case of the second model which also appears more realistic due to its symmetrical treatment of the rural and urban regions. In addition, it suggests the ability of both models to give some insights into the relative rates of natural increase and in-migration in accounting for urban population growth. This potential will be made evident in the next two papers of this series, in which the factors of urban population growth will be examined under a regime of constant rates of natural increase and migration (second paper) as well as under a regime of varying rates (third paper)