High‐Speed Railway, Knowledge Complexity and Regional Inequalities

The high‐speed railway (HSR) in China has brought tremendous economic development for cities across the country. Utilizing a dataset of over 3.9 million authorized innovated patents from 324 cities between 2000 and 2022, this study investigates the impacts of HSR on technological diversity and complexity. Employing a staggered difference‐in‐difference (DID), Propensity Score Matching (PSM) model and instrumental variable (IV) model, the analysis reveals that the introduction of HSR enables cities to diversify into new, less related, and more complex technological domains, thereby enhancing both the complexity and diversity of a city's knowledge base. However, our heterogeneity analysis suggests that HSR fosters breakthrough advancements and the adoption of more complex technologies in developed cities, but it mainly facilitates access to more related but less complex technologies in underdeveloped cities. This study underscores HSR as a crucial strategic tool for promoting technology diversification and knowledge complexity, while also highlighting the potential of HSR for exacerbating knowledge inequality among cities. The findings deepen our understanding of how regional inequality might be shaped as by technological evolution and transportation development.