Reconstructing Sustainable Development Efficiency: A Multidimensional Approach to Economic, Innovation, and Welfare Integration

Sustainable cities require an integrated development in economic growth, technological innovation, and public welfare. However, existing research tends to assess these aspects in isolation, lacking a unifying framework to capture the interconnectedness of urban sustainability systems. To fill this gap, this study constructs an integrated assessment system that conceptualizes the city as a coupled economic, innovation, and welfare system. To measure this system, we propose a novel hybrid series–parallel network slack-based measure model that advances traditional efficiency measurement by capturing sequential flows and parallel interactions between subsystems. This modeling approach not only provides a more realistic measure of the overall efficiency of urban sustainability but also supports the diagnosis and comparison of subsystem efficiencies within a unified framework. The proposed framework model is empirically applied to cities in the Yangtze River Economic Belt (YREB) in China. It is found that the sustainable development efficiency of the YREB has made significant progress from 2016 to 2020. Still, the main contribution comes from the economic subsystem, while innovation and welfare lag. Evident spatial disparities persist because downstream coastal agglomerations lead in economic and innovation performance, midstream cities have recently experienced economic momentum, and upstream cities lag in all dimensions. Most cities display imbalanced economic growth-first patterns, whereas fully balanced performers remain rare. Theoretically, this study advances sustainability science by providing a comprehensive, unified conceptual model to clarify urban sustainability dynamics. Practically, it offers policymakers a replicable diagnostic tool for developing integrated governance strategies, effectively balancing economic development with innovation investment and robust welfare provision. This framework can also be used by urban planning professionals in other rapidly developing regions to identify internal subsystem imbalances and develop targeted interventions.