The impact of innovative city construction on ecological efficiency: a quasi-natural experiment from China

With the continuous expansion of the city scale and the continuous deepening of the innovation-driven concept, an innovative city pilot program, as a momentous spatial measure of the national innovation strategy, is of great significance for China's transformation to an innovative economy. Based on the Malmquist-Luenberger index, this paper estimates the ecological efficiency of 270 prefecture-level cities in China from 2005 to 2016. At the same time, the difference in differences (DID) method is applied to test the net effect of innovative city pilots on urban ecological efficiency, and the mediating effect model is used to analyze the transmission mechanism of innovative city pilots on ecological efficiency. The empirical results show that (1) innovative city construction is conducive to improving ecological efficiency. The validity of the conclusion is proven after a series of robustness tests, such as placebo test and propensity score matching and difference models (PSM-DID). (2) The heterogeneity analysis demonstrates that the pilot policy has a more significant effect on improving ecological efficiency in cities with higher education expenditure, science and technology investment and human capital. (3) The mechanism test results indicate that innovative city pilots can have a positive impact on urban ecological efficiency through technological innovation, adjusting the industrial structure and giving full play to the direct intervention effect of the government. Accordingly, this paper argues that the pilot scope of innovative cities can be further expanded. To promote the improvement of urban ecological efficiency, the circular accumulation of knowledge and technology and the construction of a green and innovative development atmosphere need to be considered.