New infrastructure construction and carbon emission efficiency: Evidence from 270 prefecture-level cities in China

Improving carbon emission efficiency (CEE) is an essential step in balancing economic growth with environmental improvement. New infrastructure (NIS) construction, exemplified by the “Broadband China” strategy (BCS), plays a pivotal role in the process of achieving green and low-carbon development in society and the economy. This paper uses the BCS as a quasi-natural experiment, matching panel data from 270 prefecture-level cities between 2007 and 2023, and employs the difference-in-differences method to systematically assess the impact of NIS construction on CEE. The study finds that NIS construction can significantly improve CEE, and this conclusion remains valid after endogeneity tests and a series of robustness tests. Mechanism analysis indicates that the key pathways through which NIS construction enhances CEE are digital-physical integration, digital inclusive finance, industrial synergy and aggregation, and alleviating innovation resources misallocation. The heterogeneity analysis indicates that NIS construction has a more pronounced positive effect on CEE in central cities, non-traditional industrial base cities, low-energy consumption cities, non-resource-based cities, environmental protection priority cities, and transportation hub cities. The findings of this study provide theoretical support and empirical evidence tailored to China’s context for governments to leverage NIS construction to enhance CEE and thereby achieve the “dual carbon” goals on schedule.