Spatial patterns and trends of inter-city population mobility in China—Based on Baidu migration big data

Based on Baidu migration big data from the Spring Festival travel rush periods in 2022 and 2023, this study employs a combination of GIS-based spatial statistical analysis and social network analysis to analyze over 270,000 travel data records covering 297 prefecture-level cities. The research reveals that the population flow during the 2023 Spring Festival travel rush increased both in overall quantity and in the proportion of inter-provincial population flow compared to the same period in 2022. The distribution of population movement shows a distinct "southeast dense, northwest sparse" pattern, forming a diamond-shaped structure with the Bohai Sea Rim, Yangtze River Delta, Pearl River Delta, and Sichuan-Chongqing regions as the vertices. Among the most significant inter-city mobility routes are Guangzhou ↔ Foshan, Shenzhen ↔ Dongguan, Shanghai ↔ Suzhou, Xi'an ↔ Xianyang, and Beijing ↔ Langfang, which constitute the five routes with the highest flow volumes, each with its own distinctive patterns and characteristics. Significant agglomeration effects in population movement are observed, with the majority of the 40 cities experiencing higher net inflows situated in the Yangtze River Delta and Pearl River Delta regions. On the other hand, many cities in the western and northeastern regions, including some third-tier and even second-tier cities, are facing net population outflows. As the working population and major economic activities increasingly concentrate in large-scale central cities, the future development of prefecture-level cities may gradually diverge.