Research on the Impact Mechanism of Green Credit Policy on Investment Efficiency of Heavily Polluting Enterprises: A Quasi-Natural Experiment Based on the "Green Credit Guidelines"

Set against China’s push for ecological civilization and its “dual-carbon” agenda, green credit has become a pivotal policy instrument for steering financial resources toward environmentally sustainable uses, and its influence on firms’ micro-level decisions has attracted growing scholarly attention. This paper assembles a panel of Chinese A-share listed firms over 2004–2024, interprets the 2012 Green Credit Guidelines as an exogenous policy shock, and uses DID estimation alongside mediation analysis to test whether green credit improves investment efficiency among heavily polluting firms and via which pathways. The empirical evidence indicates that the policy meaningfully enhances investment efficiency among targeted firms, primarily by suppressing excessive investment. Mechanism analysis indicates that debt maturity structure plays a partial mediating role between the policy and firms’ investment efficiency; specifically, green credit policy promotes investment efficiency by reducing the scale of long-term debt financing for heavily polluting enterprises, thereby limiting inefficient investment funds. Heterogeneity analyses reveal a stronger policy effect for heavily polluting firms constrained in commercial credit, while those with greater commercial-credit capacity partially neutralize the tightening pressure through alternative financing, leading to a weaker marginal policy impact. A battery of robustness checks—including placebo exercises and propensity-score-matched DID (PSM-DID) estimations—confirms the stability of these findings. Overall, the study offers micro-level empirical support for assessing green credit outcomes and provides useful implications for refining policy design to jointly advance environmental goals and firm-level efficiency.