Urban fragmentation and innovation collaboration: Evidence from China

This paper measures the urban shape of Chinese prefecture-level cities and examines the impacts of its fragmentation on local innovation activity. Using a harmonized satellite nightlight dataset from 1999 to 2021, we delineate urban areas as polygons formed by adjacent bright grids at night. We decompose changes in a city's urban shape into two components: the dispersion of individual polygons, and the fragmentation characterized by the growing spatial separation between these polygons. Our empirical analysis reveals that deteriorating urban shape, which typically results in longer commutes for individuals to meet, is associated with fewer local patent grants, with urban fragmentation being the primary driver. Mechanism analysis reveals that intensified urban fragmentation disproportionately impedes collaborative innovation, primarily by elevating communication costs within inventor teams. These findings highlight the pivotal role of optimized urban spatial structures in fostering face-to-face interactions and knowledge spillovers essential for innovation ecosystems.