High-speed rail network and urban agglomeration economies: Research from the perspective of urban network externalities

High-speed rail (HSR) has greatly promoted cross-regional economic activities, but few studies have been conducted from the perspective of urban network externalities (UNEs). Based on data from China from 2008 to 2019, this paper constructs an HSR operation network model to study the impact of the network position (NP) on urban agglomeration economies (UAEs) by jointly employing network and econometric analysis methods. The findings suggest the following: (1) Improvements to NP significantly enhance UAEs. Improving the comprehensive NP by 1% will increase urban output per capita by 193.5–226.8 RMB. The findings hold under several robustness tests. (2) The NP's facilitation of growth in UAEs is reflected mainly in national core cities, while the impact of peripheral cities reflects a “∽-shaped” curve as their distance from each nearest neighboring core city changes. (3) From the temporal-dynamic perspective, the NP's impact on UAEs appeared one year before the HSR line was opened and was fully realized three years after the opening of the HSR. (4) Investment agglomeration and expansions in borrowed size are the main mediating mechanisms whereby NP facilitates UAEs.