距离、可达性与创新——高铁开通影响城市创新的最优作用半径研究

高铁拉近了中小城市与中心城市的时空距离,重塑了人才这一创新第一要素的空间配置,为中小城市吸纳创新资源拓宽了空间。本文采用全国284个地级市2005—2015年面板数据,将高铁开通作为准自然实验构建PSM-DID模型对“距离与城市创新”命题进行检验。实证结果表明:(1)高铁开通显著地提高了全国整体的城市创新水平;(2)高铁开通的城市创新效应呈现依“与中心城市的距离”增加而递减的特征,同时高铁开通对中心城市周边100公里范围内的城市创新提升效果不明显,表现出虹吸效应特征,综合这两种效应,最终高铁开通的城市创新效应在“与中心城市的距离”这个维度上呈现“∽”型结构特征,其作用的最优半径为距离中心城市200公里的范围;(3)高铁开通促进城市创新的机制之一是促进城市经济集聚;(4)高铁开通对城市创新的影响具有随着开通时长的增加而逐渐衰减的特征以及区域异质性。本文结论经过稳健性检验、安慰剂检验以及工具变量等处理后依然成立,可为中小城市的差异化发展和战略定位提供借鉴。

Distance,Accessibility and Innovation: A Study on the Optimal Working Radius of High-speed Railway Opening for Urban Innovation

High-speed rail has reduced the time and space distance between small and medium-sized cities and central cities,reshaping the spatial allocation of talents which is the primary factor of innovation,and broadening the space for small and medium-sized cities to absorb innovative resources.This paper adopts the 2005—2015 panel data of 284 prefecture-level cities nationwide,and uses the high-speed rail as a quasi-natural experiment to construct a PSM-DID model to test the proposition about“distance and urban innovation”.The empirical results show that:(1)the opening of high-speed rail significantly improves the overall level of urban innovation in the country;(2)the effect on urban innovation decreases as the distance from central city increases;at the same time,due to the siphon effect,the high-speed railway opening has not obvious effect on urban innovation within the 100 km range around the central city.Considering both effects,the effect of high-speed railway opening on urban innovation shows the∽-type structure in the dimension of“distance from the central city”,and its optimal working radius is within 200 km from the central city;(3)the effect varies from place to place but generally wanes as the existing high-speed rail ages;(4)one way for high-speed railway opening to improve urban innovation is by promoting urban economic agglomeration.The conclusions of this paper still hold after the treatment of robustness test,placebo test and instrumental variables,and can provide reference for the differentiated development and positioning of small and medium-sized cities.