The impact of innovative human capital agglomeration on urban green development efficiency: Based on panel data of 278 Cities in China.

• Urban green development efficiency (UGDE) was estimated with Super-SBM DEA method. • Inverted U-shaped relationship between innovative human capital agglomeration and UGDE. • Environmental regulations push back the threshold of optimal agglomeration size for human capital agglomeration. • The digital economy has a positive moderating effect on the impact of human capital agglomeration on UGDE. As a scarce and high-quality production factor, innovative human capital (IHC) significantly contributes to the innovation-driven development and low-carbon transformation of economies. Based on panel data of 278 cities in China spanning from 2011 to 2021, this paper employs Super-SBM DEA method, two-stage systematic GMM, and dynamic panel threshold model to comprehensively study the effect of innovative human capital agglomeration (IHCA) on urban green development efficiency (UGDE). The results indicate that: (1) In general, there exists an inverted U-shaped relationship between IHCA and UGDE. The Williamson hypothesis significantly influences the green development process of Chinese cities. (2) The inflection values of the inverted U-shaped curve are sensitive to different factors. Environmental regulations push back the threshold of optimal agglomeration size for IHCA, reducing the risk of the "crowding effect". (3) The digital economy has a positive moderating effect on the impact of IHCA on UGDE. The moderating effect of industrial digitization is more significant than that of digital industrialization. This paper puts forward suggestions on rational utilization of positive externalities of IHCA, appropriate enhancement of environmental regulation, and promotion if the integration of innovative talents with the digital economy. [ABSTRACT FROM AUTHOR]