高铁开通与城市创新质量——基于变处理时点DID的再检验

高铁开通有利于提升城市创新水平的观点日益流行。然而,支撑该观点的理论和经验证据并不充分。本文首先反思了高铁效应评估中普遍采纳的DID模型的作用和局限性,其次运用多种计量模型发现高铁开通对城市创新的影响具有长达五年的时滞,且主要集中在早期开通的线路,传统的DID方法的结果可能高估了高铁的作用。尽管在统计意义上高铁对城市创新具有显著影响,但是在经济意义上它并没有人们预期的那么重要。从人才流动和信息交流两条潜在机制进行分析,上述结果可能与创新效应来自资源重新配置和知识信息的非对称性外溢有关。

The Impact of High-Speed Rail on Innovation Quality:A Re-examination Based on the Stag-gered DID

The academic view that the opening of the high-speed rail is conducive to improving the level of city innovation is becoming increasingly popular. However, the theoretical and empirical evidence supporting this view is not sufficient. This article first revisits the limitations of the commonly used DID model in the evaluation of the effect of high-speed rail, and then uses panel data of 278 cities from 2000 to 2016 to demonstrate the potential impact. After considering the staggered DID model and other missing variables, we found that: First, the impact of the opening of high-speed rail on city innovation has a time lag of up to five years, and it is mainly concentrated in the early opening line; second, the results of conventional DID method and instrumental variable estimation overestimate the role of high-speed rail. Numerical simulation and variance decomposition methods further confirm that the opening of high-speed rail has a relatively small explanation for city innovation. Although high-speed rail has a significant impact on city innovation in a statistical sense, it is not as important as people expected in an economic sense. Analyzing from the two potential mechanisms of talent flow and information exchange, the above results may be related to the resource re-allocation and the asymmetric spillover of knowledge and information.