Spatial-Temporal Evolution and Multidimensional Structural Analysis of Population Growth-Decline Differentiation in the Sichuan-Chongqing Region of China

This study focuses on the Sichuan-Chongqing region of China, systematically analyzing the spatiotemporal evolution characteristics and multi-dimensional structural mechanisms of population growth and decline differentiation during 2000—2023. The results reveal a prominent "core-periphery" pattern: the core urban areas of Chengdu and Chongqing maintain positive population growth as regional agglomeration hubs, while most peripheral areas face dual pressures of declining natural growth rates and continuous outflow, with negative growth regions expanding. Using hierarchical clustering, the region is classified into six types, and a two-way fixed effects model explores population change drivers. Findings show: urbanization rate inhibits natural growth rate, while social security expenditure has a positive impact; per capita GDP, population density, and social security expenditure negatively drive net migration rate; total population growth is constrained by economic factors and agglomeration costs, with no significant direct effects of urbanization rate or social security expenditure. Correspondingly, this study proposes differentiated fertility support, optimized regional development, improved social security, high-quality urbanization, and regional collaborative governance to promote long-term balanced population development and spatial coordination in the region.