How Does the Central Environmental Supervision Reshape the Ecological Efficiency Map of China’s Cities? Micro Evidence from 285 Cities in China

The research on the effectiveness and mechanism of environmental policy is the focus of ecological policy research. This paper constructs panel data and studies the Eco-efficiency (EE) and influence mechanism of Central Environmental Supervision (CES). The Super Slacks-Based Measure (Super-SBM) model is adopted to measure EE. Difference-in-Differences (DID) methods were used for regression analysis. (1) Research shows that CES can significantly improve EE by 5.11%. A parallel trend test shows that DID is valid. (2) Endogeneity test does not find reverse causality, and Propensity Score Matching and Difference-in-Differences (PSM-DID) test does not find sample selection bias. Variable substitution test shows that the conclusions remain robust. The time bandwidth test finds that the longer CES is implemented, the better the effect. (3) CES can promote EE through industrial upgrading, technological innovation, and promoting green consumption, with relative contributions of 17.52%, 13.78%, and 14.57% respectively. (4) Heterogeneity analysis shows that CES has a significant impact on the EE of the eastern, central, and western cities, with insignificant differences, and the impact is stronger in the core cities. CES only has a significant impact on large- and medium-sized cities with a population of 3 to 10 million.