城市群多中心性与绿色发展效率——基于异质性的城镇化空间布局分析

Polycentricity and green development efficiency of urban agglomerations:spatial distribution of urbanization based on heterogeneity

城市群是城市的空间组合,是中国推进新型城镇化和践行绿色发展理念的主要空间载体,其多中心性是否有利于提升区域绿色发展效率和实现协调发展?文章利用夜间灯光数据测度了城市群的多中心性,将三大污染排放指标作为非期望产出计算了Malmquist-Luenberger动态分解指数以考察城市群绿色发展效率的跨期变化。基于2004—2018年14个重点城市群的面板数据,实证研究了城市群的多中心性对成员城市绿色发展效率的影响。研究发现:(1)城市群多中心性对成员城市的绿色发展效率存在显著的门槛效应,且东部城市群的多中心性对成员城市的绿色发展效率起到促进作用,而中部和西部城市群的多中心性则对绿色全要素生产率起到抑制作用;(2)城市群多中心性对中间位序城市的绿色发展效率产生负面效应,但是对首位城市和位序靠后的城市产生正面效应,且该效应随城市经济位序后延而递减;(3)城市群多中心性对绿色发展效率产生先促进后抑制的作用,传导机制评估发现,城市群多中心性对成员城市绿色发展效率的“倒U型”影响主要是通过知识溢出、科技创新和人力资本水平起作用。更改多中心指标、采用地形起伏度和1933年的铁路通车数据作为工具变量、更改方法为面板Tobit模型重新进行估计得到的结果没有实质性改变。基于上述发现,现阶段中国城镇化空间布局重在发展大城市和小城市之间的权衡,应综合考虑空间单元异质性,制定和实施差别化的城市群政策。

Urban agglomerations are spatial combinations of cities and the main spatial carrier for China to promote new urbanization and implement the concept of green development.Does their polycentricity help to improve the efficiency of regional green development and achieve coordinated development? This paper used satellite-monitored night light data to identify the polycentricity of each urban agglomeration in China,and used three major pollution emission indicators as undesired outputs respectively to calculate the Malmquist-Luenberger dynamic decomposition index and to examine the dynamic changes of the green development efficiency of urban agglomerations and their member cities.Based on the panel data of 14 key urban agglomerations from 2004 to 2018 to study the impact of polycentricity on the green development efficiency of member cities,this research found that:(1) The polycentricity of urban agglomerations had a significant threshold effect on the green development efficiency of member cities,and the improvement of polycentricity could improve the green total factor productivity of eastern urban agglomerations,but it had a negative effect on central and western urban agglomerations.(2) Polycentricity had an ‘inverted U-shaped’ influence on the urban agglomerations.The transmission mechanism found that the ‘inverted U-shaped’ influence was mainly achieved through knowledge spillover,technological innovation,and human capital.(3) The improvement of polycentricity had a negative effect on the green total factor productivity of medium-sized cities,but a positive effect on the green total factor productivity of cities in the lower rank,and its effect gradually decreased with the fall of the city’s economic rank.After changing the polycentricity index,using topographic relief and data of railway opening in 1933 as instrumental variables,and using the panel Tobit model and panel threshold model,the results obtained were basically the same,which confirmed the robustness of the results.Therefore,at the present stage,with China’s spatial distribution of urbanization focusing on the tradeoff between the development of big cities and small cities,the heterogeneity of spatial units should be comprehensively considered,and differential urban agglomeration policies should be formulated and implemented.