The principal aim of this reader is to stimulate debate and continued research on the long-term trends of population migration. This it does by highlighting the similarities and differences in the fundamental characteristics of demographic trends in developed and less developed countries. It offers historical perspectives on the beginning of counterurbanization; an overview of contradicting explanations for spatial concentration and deconcentration trends and attempts to integrate the largely compartmentalized migration theory which has developed in the First and Third Worlds over the past twenty-five years.Part 1 combines the views of leading scholars, from several disciplines, in a manner which portrays the evolution of thought in the fields of spatial population concentration and deconcentration. Part 2 brings together a body of contributions debating the dominance of population concentration and deconcentration at different phases of development. Part 3 extends the conceptual framework of the debate by highlighting overlapping views and thus enables the reader to determine the relevancy of related theoretical concepts that explain long term migration trends in both worlds. Based on an analysis of long term migration trends, the book ends with a prognosis of future trends.