The impact of digital infrastructure construction on carbon emission efficiency: Considering the role of central cities

This paper delineates the impact of digital infrastructure construction (DIC) on carbon emission efficiency (CEE) within the ambit of China's "Broadband China" pilot policy (BCP). A quasi-natural experimental framework reveals direct effects, indirect influences, non-linear relationships, and spatial heterogeneity of DIC on CEE. The research distills several pivotal insights: (1) DIC exerts a markedly positive impact on CEE, as evidenced by comprehensive robustness analyses. (2) The digital service industry agglomeration and green technology innovation act as key mechanisms through which DIC influences CEE. (3) The intensity of BCP exhibits an "inverted U-shaped" relationship with CEE. As the level of CEE increases, the impact of DIC on CEE gradually rises, demonstrating a marginal increasing effect. (4) The spatial spillover effects of DIC on CEE vary with increasing distance, revealing a dichotomy: an "agglomeration shadow" within 200 km of policy pilot cities and a pronounced stimulative effect on CEE within a 200–300 km radius. (5) The efficacy of DIC in enhancing CEE is augmented by proximity to central cities, with the optimal radius of influence for central cities determined to be 200 kilometers, beyond which a diminishing gradient effect is observed, forming a "core-peripheral" spatial pattern. The findings endorse the strategic augmentation of digital infrastructure as a lever for economic and environmental co-benefits, steering towards carbon neutrality and equitable regional development.