Economic spatial polarization is a manifestation of unbalanced urban development. To study the unbalanced development of Chinese cities, this paper selects 41 cities in the Yangtze River Delta (YRD) region, introduces the polarization index and exploratory spatio-temporal analysis to portray their spatio-temporal evolution process, and analyzes the differences in spatial polarization patterns of economic development in three dimensions of economic quantity, quality, and structure. Finally, we use the geographic detector model to explore the driving factors and then propose corresponding policy recommendations. The results show that: (1) the degree of difference in economic development in the YRD region narrowed from 2000 to 2019, and the spatial polarization level of urban economic development showed a fluctuating downward trend, among which the spatial polarization level of the economic structure dimension has been increasing. (2) In terms of spatial distribution, the "Yangtze River Delta urban agglomeration" has economic spatial polarization in the YRD region has become the peak contiguous zone, and the spatial polarization of economic quantity and quality dimensions has formed a "polycentric" pattern, while the spatial polarization of economic structure dimensions shows a stable "one core, multiple sub-center" distribution. (3) From the evolution of spatial polarization, most cities have strong spatial locking characteristics without a transition. Spatially positive polarized are concentrated in the YRD urban agglomeration, and the inter-city neighboring relations are mainly positive synergistic growth, while the negatively polarized cities are mostly distributed in the peripheral areas of the YRD and the neighboring relations are negative synergistic growth. At the same time, the spatially positive polarization effect of the economic quantity dimension and the spatially negative polarization effect of the economic structure dimension among cities are more significant. (4) The economic spatial polarization in the YRD region is mainly dominated by market prosperity and urbanization level, while the driving effect of scientific and technological innovation development on the urban economy has also been expanding in recent years. Promoting the reasonable allocation of marketization, urbanization, and technology among cities with positive and negative spatial polarization in the future will contribute to balanced urban and regional economic development in a coordinated and orderly manner.
Keywords: Yangtze River Delta (YRD) region; economic development; regional coordination; spatial and temporal evolution; spatial polarization.