## 1 Introduction  
Since the dawn of mankind, migration has been a crucial strategy for survival and development [1]. From the earliest days of settling near water and fertile land to the current global population migration, the depth and breadth of human migration have expanded with the development of productive forces, and the frequency of migration has also increased [2]. The rapid development of transportation and information technology, particularly since the industrial revolution, has significantly reduced temporal and spatial distances worldwide, facilitating urban-rural, regional and even long-distance transnational migration [3, 4]. In recent decades, although public health emergencies such as SARS and COVID-19 have temporarily halted large-scale population migration, migration has quickly resumed as the epidemics have subsided [5, 6, 7]. Population migration is a \"double-edged sword\" that profoundly influences the status and trends of regional development. For destination regions, migration enhances labor conditions and promotes the concentration of production factors, such as talent and capital, thereby boosting regional development [8; 9]. However, it can also increase the pressure on transportation, housing, and employment while introducing challenges such as racial tensions and social conflicts [10; 11]. For source regions, migration alleviates population pressure and human-environment conflicts and strengthens their economic, social, scientific, and cultural ties with the outside world [12]. However, it can also lead to problems such as brain drain, labor shortages, and the erosion of local culture [13; 14], especially in rural areas, where large-scale population exodus exacerbates rural decline [15]. Given the important role of population migration in regional development, scholars in demography, economics, statistics, and sociology have conducted extensive research on this issue and developed far-reaching theories and models, including the push-pull theory [16], the gravity model [17], and the labor migration model [18]. While migration is a global phenomenon, its patterns and driving forces exhibit significant variations across countries, particularly in rapidly transforming economies such as China. In China, population migration is closely tied to the hukou system (the household registration system in China) [19]. In the early years of the PRC, the hukou system was established to stabilize domestic public order, among other objectives. Between 1959 and 1978, the hukou system was consolidated by categorizing households as \"agricultural\" or \"non-agricultural\", dividing the population into rural and urban residents. Strict transfer procedures and legal restrictions controlled population migration, confining rural residents to agricultural work and restricting their access to urban areas [20; 21; 22]. As China's reform and opening up in 1978 progressed, the huge labor demand generated by the economic development necessitated the reforms to the hukou system to achieve the optimal allocation of production factors such as labor on a larger scale [23; 24]. In this context, farmers going out to work or do business were allowed to provide their own food and settle in towns, marking the beginning of population migration. Subsequently, the introduction of a series of policies and measures, combined with rapid industrialization and urbanization, deepened the hukou system reform and triggered a wave of domestic population migration, and the scale of population migration has continued to rise rapidly [25]. The 2020 national population census confirmed China's historic transition from a low-mobility \"rural China\" to a high-mobility \"migrant China\" [26]. China's massive population migration has reshaped the country's regional development pattern and drawn widespread attention from academia.