Regional Synergy in the Economic Transformation of Land-Border Ports and Its Impact on Border Residents’ Income—Evidence from Guangxi, China

The transformation of land-border ports from transit channels into regional hubs is increasingly seen as a way to support inclusive growth in frontier regions. Yet port expansion does not automatically improve local livelihoods. Whether port-led development is associated with income gains for rural residents in border counties depends on how cross-jurisdictional public goods are supplied, coordinated, and absorbed. Drawing on collective-action theory and regional public-goods theory, this study develops a two-tier analytical framework that distinguishes regional synergy from county response. Using panel data for seven counties along the China–Vietnam border in Guangxi from 2008 to 2023 and supplementary field research, we apply two-way fixed-effects models, control-function checks, mediation tests, and port-size heterogeneity analysis. Three main findings emerge. First, regional synergy and county response, proxied by Region_BPEDI and Dev_BPEDI, are both positively associated with the logarithm of rural per-capita disposable income in border counties. A one-standard-deviation comparison shows that the estimated association of Region_BPEDI is about 2.5 times that of Dev_BPEDI. Second, industrial-structure upgrading shows the strongest mediating pattern, while infrastructure connectivity and financial development depend more on cross-tier coordination. Third, large ports such as Dongxing and Pingxiang are better positioned to benefit from regional synergy, whereas medium and small ports rely more on niche-based differentiation. The results suggest that hub-oriented border transformation may benefit from multi-level institutional collaboration, place-based industrial matching, and tailored financial instruments. Field evidence also indicates that smart customs clearance, low-carbon logistics, and cross-border environmental coordination are becoming important sustainability dimensions of regional synergy. The study provides a diagnostic framework for evaluating border-port reforms along the Belt and Road and ASEAN economic corridors.