区域一体化与城市创新：基于长三角扩容的准自然实验

随着我国城市进入都市圈发展的新时代，区域一体化对城市创新产生了广泛而深刻的影响。从创新资源流动整合、知识技术溢出和市场规模扩大等维度深入分析区域一体化对城市创新的潜在作用机制，将长三角扩容作为一项准自然实验，以2003-2018年中国内地283个地级市为样本数据，综合利用合成控制法和PSM-DID模型对两者关系进行实证检验。结果发现：①整体而言，长三角扩容能够显著促进城市创新水平提升。从不同区域看，长三角扩容对原位和新进城市创新水平均有显著促进作用，且对新进城市的影响大于原位城市；②异质性分析结果表明，扩容政策对科创走廊城市创新水平的提升作用强于非科创走廊城市，同时区域通达性改善也能够明显强化扩容对城市创新的政策效应；③扩容政策对城市创新的作用呈现出边际效应递减趋势。研究结论对推进长三角一体化发展、深化区域创新合作、建设长三角创新驱动示范带具有重要指导意义。

Regional Integration and Urban Innovation:based on the Quasi-natural Experiment of the Enlargement in Yangtze River Delta

As Chinese cities entered a new era of metropolitan region development, regional integration is having a profound and extensive impact on urban innovation. This study deeply analyzed the potential mechanism of regional integration for urban innovation from the aspects of the flow and integration of innovation resource, knowledge technology spillover and market scale expansion. Moreover, this paper took the panel data of 283 cities in china from 2003 to 2018 as samples, and regarded the enlargement in Yangtze River Delta as a quasi-natural experiment. In addition, it empirically analyzed the relationship between the enlargement in Yangtze River Delta and urban innovation by using synthetic control method and PSM-DID model. The results showed that: ①Overall, the enlargement of the Yangtze River Delta significantly promoted the improvement of whole cities 'urban innovation. And in terms of different regions, the expansion also significantly improved the urban innovation of incumbent cities and new cities, but new cities' improvement was greater than the influence of incumbent cities.②The results of heterogeneity analysis showed that the expansion policy had a stronger effect on the urban innovation cities which located in Scientific Innovation Corridor than other cities, meanwhile, the improvement of regional accessibility can also significantly enhance the expansion policy's effect on urban innovation.③Further analysis found that the effect of expansion policy on urban innovation shows a trend of diminishing marginal effect. The results of this study is of great significance to promote the integrated development of the Yangtze River Delta, deepen regional innovation cooperation, and develop the innovative demonstration in the Yangtze River Delta region.