Digital Infrastructure, Green Total Factor Productivity, and Sustainable Development in the Yangtze River Economic Belt: Evidence from the Broadband China Pilot Policy

This study examines whether digital infrastructure contributes to sustainable development by improving green total factor productivity (GTFP)—a comprehensive measure that jointly evaluates economic output and environmental performance—in the Yangtze River Economic Belt. We exploit the staggered implementation of the “Broadband China” pilot policy as a quasi-natural experiment and estimate its effects using panel data for 107 prefecture-level cities from 2010 to 2022. The empirical strategy combines a staggered difference-in-differences design with an event study framework. The baseline results show that the average treatment effect for the full sample is positive but not statistically significant at conventional levels under standard TWFE estimation; however, the Sun–Abraham interaction-weighted estimator confirms a significant positive effect (ATT = 0.080, p < 0.05), and the Goodman-Bacon decomposition shows that the TWFE estimate is driven primarily by clean comparisons (91% weight, 0% negative weights). Further analysis reveals substantial regional heterogeneity. The estimated effect is significantly positive in the central region (0.171, p < 0.05), positive but not significant in the eastern region (0.097), and negligible in the western region (−0.042). A similar pattern emerges across income groups: digital infrastructure generates significant gains in GTFP in high- and middle-income cities, whereas the effect is not identifiable in low-income cities. These results remain robust to propensity score matching, placebo tests, alternative specifications, and alternative measures. Exploratory mechanism analysis provides limited evidence that technological innovation and industrial upgrading mediate the effect of digital infrastructure on GTFP within the sample period, though the causal interpretation of mediation is constrained by the sequential ignorability assumption. The findings suggest that the environmental returns to digital infrastructure depend on local complementary conditions, especially human capital, institutional capacity, and industrial foundations. These results imply that digital infrastructure policy should be differentiated across regions rather than implemented uniformly. By demonstrating that the environmental returns to digital infrastructure are conditional on local complementary conditions, this study contributes to the sustainability literature by providing a framework for quantifying and monitoring the sustainability impacts of digital infrastructure policies, with implications for sustainable development strategies in developing economies.