交通设施改善、市场集聚效应与城市人口增长差异

Transportation Infrastructure Improvement, Agglomeration Effect,and Urban Population Growth Divergence

针对中国城市人口增长率和城市规模明显分化的现象,本文从向心力的集聚效应和离心力的通勤成本视角进行研究。理论模型和1990—2020年全国人口普查数据的回归结果显示,地铁等交通设施改善和基于市场潜力的消费集聚效应会增大均衡时城市规模,区位基础等本地特征因素也会影响均衡城市规模。稳健性和异质性检验表明,交通设施的改善驱动高等级大城市人口的持续增长,来自市场潜力的集聚效应是中小城市人口增长的关键因素。进一步分解关键解释变量的计量结果表明,城市群,特别是都市圈的中小城市的人口快速增长得益于圈层结构中市场潜力带来的集聚效应,而内陆和东北的孤立中小城市因市场潜力弱而人口增长缓慢。机制分析结果显示,市场潜力通过增加产品需求和提升工资水平、交通设施改善通过提高有效劳动力数量和提升公共服务水平,吸引人口流入并推动人口增长,且房价调节关键解释变量与人口增长的关系。为促进城镇体系协调发展,国家应构建“中心城市-都市圈-城市群+外围中小城市”多层次空间格局,优化区域空间功能分工体系。

After three decades of urbanization in China,much effort should be made to address the imbalance in the development of cities,especially in the rate of urban population growth and the size of cities.Therefore,this paper explains the causes of the differences in city size growth from the perspectives of the agglomeration effect of centripetal force and the commuting cost of centrifugal force.Based on the national census data from 1990 to 2020,the empirical findings prove the main inferences of the theoretical model.The robustness and heterogeneity tests demonstrate that the continual population growth in high administrative level cities is primarily driven by transportation infrastructure improvement,while the agglomeration effect from market potential drives population growth in small and medium-sized cities.By decomposing key explanatory variables,the results indicate that the rapid population growth of small and medium-sized cities in urban agglomerations,especially in metropolitan areas,benefits from the agglomeration effect brought by market potential under the circling-layering economy structure.However,isolated small and medium-sized cities in the inland and northeast regions are experiencing slow population growth owing to weak market potential.The mechanism analysis reveals that enhanced market potential increases product demand and raises wage levels.In contrast,transportation infrastructure improvement enhances the effective labor force and public service level,attracting inbound migration of outsiders and driving population growth.In addition,house price positively moderates the population growth effect of market potential and negatively moderates that of transportation infrastructure improvement.Therefore,this paper proposes some targeted recommendations,such as promoting high-quality growth of large cities,stabilizing and improving the economic levels and population carrying capacity of small and medium-sized cities,and fostering and consolidating metropolitan areas and urban clusters anchored by central cities to construct a coordinated development pattern among large,medium,and small-sized cities.The contributions of this paper are as follows.First,by integrating the intra-city and inter-city general equilibrium models,it constructs a theoretical model in which transportation infrastructure improvement and the market agglomeration effect jointly affect the city size at equilibrium.Second,it adopts a more scientific method to measure the market aggregation effect,considering the effects of transport distance and time on trade costs and further decomposition of market potential into four dimensions using Taylor expansion.Third,after testing the general characteristics of the impact of transportation infrastructure improvement and agglomeration effect on cities,it reveals the differences in their impact on different types of cities and the mechanisms.