time：2023-01-01
Siwei Cao, Guangrong Ma, Hao Mao
The expansion of high-speed railway (HSR) networks has significantly transformed intercity transportation, increasing travel frequency and facilitating face-to-face interactions. This study investigates whether such reductions in travel costs mitigate the geographical concentration of knowledge spillovers. Using China's rapid HSR expansion as a natural experiment, we employ patent citations as a proxy for knowledge spillovers and find that inventors increasingly rely on distant knowledge after gaining rail access. Additionally, cities newly connected to HSR experience substantial improvements in innovation performance.
Historically, innovation activities have been highly concentrated in specific cities or zones, primarily due to the critical role of face-to-face communication in knowledge diffusion. However, advancements in modern transportation, especially the development of HSR, have made intercity interactions more frequent. HSR reduces both physical and economic barriers to travel, allowing tacit knowledge to flow more easily across cities, which may reshape the spatial distribution of knowledge spillovers. Using panel data analysis and an instrumental variable approach, this study identifies a causal impact of HSR on knowledge diffusion. The findings indicate that after HSR connection, the geographical range of patent citations expands significantly, particularly for long-distance connections. This effect is attributed to the time-saving nature of HSR, which operates at a consistently high speed, making its contribution to knowledge spillovers more pronounced over longer distances.
Beyond patent citations, this study also examines city-level innovation performance. Results show that HSR access increases both the number of new patent applications and the average number of citations per patent, reflecting an improvement in innovation quality. Additionally, technological diversity in newly connected cities increases, indicating enhanced cross-sector knowledge exchange. These findings further reinforce the positive role of HSR in facilitating knowledge spillovers.
The study’s conclusions hold important policy implications. The geographical scope of knowledge spillovers determines which level of government—local, regional, or central—should take primary responsibility for managing technological externalities. If knowledge spillovers are highly localized, local governments play a greater role; however, if transportation improvements expand knowledge diffusion beyond individual cities, regional or central governments must take a more active role in optimizing R&D incentives. The findings suggest that HSR development not only improves transportation efficiency but also fosters intercity knowledge exchange, thereby reducing the spatial constraints of knowledge spillovers. Accordingly, governments should consider the impact of transportation infrastructure investment on innovation diffusion to maximize its role in promoting knowledge dissemination and technological advancement.