Effect and Mechanism of Economic Circulation in the Middle and Lower Reaches of the Yellow River: Multiregional Input–Output Model and Industrial Complex Network Approaches

China has implemented the Yellow River strategy, and the middle and lower reaches of the Yellow River (MLYR) play an important role in promoting the sustainable economic growth of China. However, the economic circulation of the MLYR is constricted by the imbalance and heterogeneity in the economy in the regions, and it is necessary to explore how economic circulation and sustainable development in the MLYR can be improved. In this study, based on the multiregional input–output tables for 2012 and 2017, we developed a MLYR multiregional input–output model; applied indicators, such as intraregional multiplier, interregional feedback, and spillover, to measure economic circulation effects; further developed the industrial circular network; and designed indicators of cycle length distribution, average cycle correlation, influence of the industrial cycle, and interactions of the weighted cycle to analyze the industrial circulation mechanism in the MLYR. We also analyzed the spatial and industrial structures of the economic circulation flows. The results show that economic linkages have been strengthened to a certain extent, but the imbalance in economic circulation is still prominent, and the imbalanced circular effects are determined by the characteristics of the cycles in the MLYR. The empirical findings contribute to several aspects of the theory of imbalanced economic development and provide an important perspective on, and feasible path for, achieving economic development. We suggest that policymakers should build a multi-dimensional innovation cooperation system, improve the digital connectivity of regions, and promote the green and low-carbon development of industry and the application of new energy technologies to achieve balanced, common, and sustainable economic development in the MLYR.