Spatial and temporal distribution of population in urban agglomerations changes in China

The spatial distribution of the urban agglomeration population has changed increasingly in rapid urbanization. It affects the urban economy, environment, transportation, and so on. Therefore, it is of great significance to understand the changes in the spatial distribution of population in urban agglomerations. This study used methods such as population center of gravity migration and Gini coefficient to explore changes in the spatial distribution of urban populations. The study found that the population center of the Beijing-Tianjin-Hebei urban agglomeration first migrated toward Beijing and then away from Beijing. During this process, the Gini coefficient increased from 0.62 to 0.64 and then decreased to 0.58, indicating that the population balance of the urban agglomeration firstly increased and then decreased. This result is consistent with the conclusion that we have established a simulated urban agglomeration for theoretical derivation. That is: in the early stage of urban agglomeration development, the population migrated to the central city; as the population of the central city became saturated, the urban agglomeration developed to a mature stage, and the population began to migrate to the peripheral cities. In this process, the population distribution center of urban agglomeration gradually shifted from central towns to peripheral towns. The degree of equilibrium in the spatial distribution of population has undergone an inverted u-shaped transition from non-equilibrium to equilibrium.