高铁开通提升了城市绿色发展效率吗——基于双重差分模型的实证检验

以高铁开通这一事件构造准自然实验，基于2006~2017年中国271个地级市的平衡面板数据，首先通过数据包络分析法测算城市绿色发展效率，进而使用双重差分模型和中介效应模型检验高铁开通对城市绿色发展效率的影响及作用机制。研究发现：（1）整体上，高铁开通显著提升了城市绿色发展效率。在缓解内生性问题和进行多项稳健性检验后，这一结论依然成立。从动态效应上看，高铁对城市绿色发展效率的拉动呈逐年上升的趋势。（2）机制分析表明，高铁开通凭借创新效应、结构效应与配置效应提升了城市绿色发展效率，其中创新效应发挥的作用最强，而结构效应的影响较弱。（3）异质性研究发现，高铁开通对城市绿色发展效率的拉动作用在东部地区和大中型城市更为显著。（4）基于地理距离圈层的扩展分析表明，高铁开通对不同圈层内城市绿色发展效率的促进效应呈"倒U"型变化趋势，且在距中心城市200 km处达到最大。

Does High-Speed Railway Improve the Efficiency of Urban Green Development-An Empirical Test Based on Difference in Difference Model

Based on the balanced panel data of 271 prefecture level cities in China from 2006 to 2017, this paper uses the data envelopment analysis method to measure the efficiency of urban green development, and then uses the difference in difference model and the intermediary effect model to test the impact and mechanism of high-speed rail on urban green development efficiency. The results show that:(1) on the whole, the opening of high-speed rail has significantly improved the efficiency of urban green development. This conclusion is still valid after alleviating endogenous problems and carrying out a number of robustness tests. From the perspective of dynamic effect, the pull of high-speed rail to urban green development efficiency is increasing year by year. (2) The mechanism analysis shows that the opening of high-speed rail improves the efficiency of urban green development by means of innovation effect, structural effect and configuration effect, among which innovation effect plays the strongest role, while structural effect has a weak impact. (3) The heterogeneity study found that the pull effect of high-speed rail on urban green development efficiency is more significant in the eastern region and large and medium-sized cities. (4) Based on the analysis of the expansion of geographical distance circle, it shows that the promotion effect of the opening of high-speed railway on the green development efficiency of cities in different circles shows an inverted U-shaped trend, and reaches the maximum at 200 km away from the central city.