Migration and the Dynamics of Multiregional Population Systems

This paper gives a personal perspective on some models of national settlement systems, and draws attention to the importance of population migration within these models. It includes a discussion of the inadequacies of current models of interurban migration for the analysis of the dynamic interaction between the demographic and economic growth sectors of a system of postindustrìal cities. The paper is not, however, a review; instead, the aim is to obtain insights on how to progress towards a framework and a strategy for research that will usefully contribute to the analysis of national settlement policy. Section 2 considers recent developments in multiregional demographic analysis and argues that these are of limited usefulness unless they are integrated with models of regional economic growth. Results are presented which show that multiregional demographic analyses are extremely sensitive to the assumptions about migration movements. Section 3 outlines three models which interrelate demographic and economic growth, and stresses the links between the two sectors. Each model considers population migration a key link, and two of them assume that the movement of workers provides an equilibrating mechanism between labour supply and demand. Section 4 questions the validity of this traditional approach to migration and argues that, for a system of postindustrial cities, a new approach is required (Morrison, 1973; Renshaw, 1972; Cordey-Hayes and Gleave, 1973; 1974). A conceptual framework, which emphasizes information flows, differential mobility, and inhomogeneity of labour, is sketched. The final section concludes that no single model or approach provides a royal road to models of national settlement systems, owing to gaps in our understanding of the dynamics of interactions amongst cities. It is suggested that a hierarchy of models should be developed at varying levels of approximation.