City-size distributions and the world urban system in the twentieth century

"In this paper we trace and interpret changes in the geographical pattern and city-size distribution of the world's largest cities in the twentieth century. Since 1900 the geographical distribution of these cities has become increasingly dispersed; their city-size distribution by rank was nearly linear in 1900 and 1940, and convex in 1980. We interpret the convex distribution which emerged following World War 2 as reflecting an economically integrated but politically and demographically partitioned global urban system. Our interpretation of changes in size distribution of cities emphasizes demographic considerations, largely neglected in previous investigations, including migration and relative rates of population change."