The impact of upgrading administrative rank on regional innovation from an agglomeration perspective: a quasi-natural experiment based on the establishment of Chongqing as a province-level municipality

Introduction Administrative rank, as an intuitive manifestation of a region’s political capital, significantly influences regional agglomeration capacity and innovative development. Methods This study utilizes Chongqing’s promotion to a province-level municipality as a quasi-natural experiment, employing panel data from 219 counties in Sichuan and Chongqing (1992–2010) and applying the difference-in-differences (DID) method to evaluate the impact of administrative rank upgrades on regional innovation. Results The findings show: (1) Administrative rank upgrade significantly enhances regional innovation with long-term positive effects; (2) Spatial spillover effects follow an inverted U-shape, peaking at 60 km and remaining significant within 30–120 km; (3) Population agglomeration and economic agglomeration are key mechanisms, with economic agglomeration having greater impact. Discussion This study provides theoretical insights for optimizing administrative resource allocation, advancing institutional reform, and refining national innovation-driven development strategies.