Has the construction of national central cities improved the carbon productivity of urban cluster? Empirical evidence from China

Abstract

The national central city is the highest level within China's urban system, bearing the significant responsibility of leading national and regional coordinated development. Based on panel data from 19 city clusters and 207 cities in China spanning the years 2003 to 2019, we treat China's national central city construction policy as a quasi-natural experiment. It employs a difference-in-differences model and a mediation effects model to evaluate the impact mechanism of national central city construction on urban cluster carbon productivity. The result shows that, firstly, the national central city construction significantly enhances urban cluster carbon productivity, a result robustly validated through various sensitivity tests. Secondly, heterogeneity analysis demonstrates that national central city construction exerts a positive influence on the carbon productivity of city clusters in the eastern and central regions. Notably, the effect is more pronounced in the eastern region, whereas it exhibits a distinct inhibitory effect on city clusters in the western region. Overall, the policy effect follows a "U"-shaped trend from west to east. Moreover, a positive correlation emerges between policy effects and city scale, implying that larger cities within city clusters manifest more prominent policy effects stemming from national central city construction. Thirdly, the mechanism of action suggests that national central city construction primarily enhances carbon productivity by augmenting technological innovation capabilities and expediting functional division within urban clusters. Based on the aforementioned findings, it is recommended to actively advance national central city construction, further elevate the technological level of national central cities, and sustain the role of national central cities in driving functional specialization within urban clusters.