Borrowed size and borrowed administrative power: Effects of high-speed rail network on industrial upgrading and variegated externalities in the Yangtze River Delta, China

While the externalities of urban size on regional transportation infrastructure effects have been extensively discussed, the role of urban administrative power has received comparatively less scholarly attention. This study delves into the impact of high-speed rail (HSR) development on urban industrial upgrading and regional development, focusing on both economic and administrative externalities. By applying the concepts of ‘borrowed size’ and ‘agglomeration shadow,’ we analyze the effects of HSR on industrial upgrading in the Yangtze River Delta (YRD) region using panel data from 199 county-level units between 2000 and 2017. Employing multi-stage difference-in-differences (DID) and difference-in-difference-in-differences (DDD) models, our findings reveal that HSR significantly catalyzes industrial upgrading in the YRD, with a notable reduction in the output value of the secondary sector by 4.4 % and an expansion of the tertiary sector by 7.4 %. Additionally, this study indicates a positive correlation between urban size and manufacturing sector exit, while administrative power enhances the service sector's concentration in HSR-connected regions. These findings not only contribute to the existing body of scholarship on HSR's role in industrial upgrading but also advance a novel methodological approach that bridges transport geography and urban political economy through the lens of transport infrastructure as a mediating mechanism.