Environmental regulation effect on green total factor productivity in the Yangtze River Economic Belt

As a typical watershed ecological economy in China, the Yangtze River Economic Belt has two equally important objectives, namely ecological protection and economic development. Improving green total factor productivity is an essential approach to achieve these two objectives and promote sustainable growth in this area as well as the whole country. Therefore, this study explores the impact of environmental regulation on green total factor productivity with a panel data of 108 cities in the Yangtze River Economic Belt between 2003 and 2019. We first adopt the super slacks-based measure model to estimate city-level green total factor productivity. With kernel density curve, we find that green total factor productivity shows a downward pressure, and its absolute difference among cities shows a narrowing trend. Trend surface analysis displays an inverted U-shaped as well as a U-shaped spatial structures of green total factor productivity in the north-south as well as east-west directions, respectively. By using Spatial Durbin Model, we find a U-shaped direct impact of environmental regulation on green total factor productivity for the entire sample and three subsamples. For an indirect effect, environmental regulation has a positive spatial spill-over impact in the entire area; an insignificant effect in upstream and midstream areas; and an inverted U-shaped spatial spill-over in downstream area. Besides, we utilize threshold effect analysis to explore the impacts of technology innovation. The results show a single-threshold effect of technology innovation and the promotion effect decreases when technology innovation expenditure exceeds the threshold value. Based on our research findings, we suggest that the authorities should adhere to implementing and increasing the intensity of environmental regulation, so as to achieve better policy results. Moreover, local governments should keep technological innovation expenditure at a reasonable level to maximize the promoting effect of environmental regulation on green total factor productivity.