The impact of environmental policy mix characteristics on green innovation efficiency

Local environmental policies have a significant impact on promoting regional green innovation. A thorough exploration of the relationship between the characteristics of environmental policy combinations and green innovation efficiency is crucial for achieving the “dual carbon” goals. This paper, based on grounded theory, constructs a dual-mode network of “local government—environmental policy” and evaluates the diversity and homogeneity of environmental policy combinations. Additionally, the complexity index is iteratively calculated using a nonlinear co-evolutionary approach. We demonstrate that the relationship between environmental policy mix complexity and green innovation efficiency is “inverted U-shaped”. Our findings also reveal that the diversity of environmental policy mix has a significant positive effect on the green innovation efficiency, while the homogeneity has a negative impact. Additionally, we identify substantial regional heterogeneity in the impact of environmental policy implementation. In coastal, economically developed, and resource-based regions, the complexity of the environmental policy mix positively influences green innovation efficiency, with the strongest effect observed in Shanghai—a representative coastal and economically advanced city. Conversely, in inland, economically underdeveloped, and non-resource-based regions, the effect is generally insignificant, with Guizhou—an economically weaker inland province—exhibiting the least impact. Based on the research findings, local governments should strengthen communication and information exchange, actively explore innovative policies suited to local conditions, enhance policy diversity, and maintain the environmental policy complexity index at its optimal level. This paper aims to enrich the theoretical framework for the quantitative research methods of environmental policy mixes, promoting the scientific formulation of environmental policies.