Chapter 35 Trends in sizes and structures of urban areas This chapter reviews the literature dealing with systems of cities and the patterns of development within such systems. It starts with the longstanding question of the distribution of city sizes both in relation to how this distribution can be described and given the form that it takes how that form can be explained. Such explanations frequently invoke various sorts of agglomeration economies and so some of the literature relating to these is included here. The chapter then surveys the literature that examines patterns of development within urban systems and then work at a more disaggregated level on suburbanisation. The chapter concludes with a summary of research into recent patterns of urbanisation including relative recentralisation.