Port group integration and regional high-quality economic development: Mechanisms and spatial effects

Based on the panel data of 60 coastal ports and 297 prefecture-level cities in China from 2013 to 2022, this study constructed the Port Group Integration Index (PGII) and the High-Quality Economic Development Index (HQEDI) to systematically examine the mechanisms and spatial heterogeneity through which port group integration influences high-quality development in their hinterlands. A multi-dimensional analytical framework is constructed based on the application of two-way fixed-effect model, mediating effect test, dynamic spatial panel model, nonlinear test model and a series of robustness tests. Results indicate that port group integration exerts a significant inverted U-shaped impact on regional economic performance, with an optimal threshold at PGII≈0.556. The transmission channels are multifaceted, with industrial upgrading and market vitality serving as positive mediators, while technological innovation shows a significant crowding-out effect in early integration stages. Dynamic and spatial analysis confirm that integration benefits accumulate over the long term and are strongly driven by network externalities and spillover effects. This study provides a systematic theoretical basis and empirical reference for the temporal arrangement, spatial layout and mechanism design of the port group integration policy, supporting coordinated, high-quality regional development.