Changes of economic development disparities in the Yangtze River Delta and policy effect analysis from the perspective of Yangtze River Delta integration expansion

Regional development disparity is an eternal research topic of economic geography. Taking the Yangtze River Delta, a high-quality integrated development demonstration area, as the research object, this study examined the dynamic change of regional economic development disparities during the expansion of the spatial scope of Yangtze River Delta integration, and further used the difference-in-differences method, mediation effect model, and spatial Durbin model to empirically test the impact of the implementation of the Yangtze River Delta integration policy on regional economic development disparities and the mechanism of impact. The main conclusions are as follows: 1) The expansion of the spatial scope of Yangtze River Delta integration has caused an increase in the economic development disparity within the region. However, with the continuous promotion of Yangtze River Delta integration, the imbalance of economic development within the region has been effectively improved, and it showed a long-term trend of narrowing. 2) From the perspective of geographic locations, the Yangtze River Delta integration policy has played an important role in promoting the development of remote and economically weak areas within the planning scope. 3) From the regional boundary perspective, the Yangtze River Delta integration policy has had a significant border effect, reducing the strategic and transportation positions of cities with similar geographic locations around the Yangtze River Delta that are not within the scope of the integration plan, and having a negative impact on their development. 4) Mechanism analysis showed that the implementation of the Yangtze River Delta integration policy has narrowed the regional economic development disparity mainly by transaction cost effect, technology spillover effect, and industrial optimization effect. Under the background of building a national high-quality development model area and a world-class urban agglomeration, this study provides a theoretical support and empirical evidence for further improving the framework of Yangtze River Delta integration, and exploring replicable regional high-quality integrated development models.