Urban scaling and diffusion of knowledge recombination in Chinese cities, 1991–2020

Using invention patent data for 286 Chinese cities between 1991 and 2020, this study examines how urban technological diversity shapes the creation and diffusion of new knowledge combinations. First, urban scaling analyses reveal a strongly super-linear relationship between technological diversity and the number of new combinations, with the scaling exponent rising from just above 1.0 in the early 1990s to over 2.2 by 2020, indicating increasing returns to technological diversity in urban innovation systems. Cities with broader technological portfolios therefore generate disproportionately more new knowledge combinations. The analysis also distinguishes between types of recombination. Atypical combinations that connect cognitively distant technologies show stronger scaling effects than typical combinations, underscoring the importance of diverse cities in generating novel and potentially breakthrough innovations. Second, the paper examines how newly generated combinations diffuse across cities using event-history models. Results show that diffusion is strongly shaped by multi-dimensional proximity: geographic distance reduces the likelihood of adoption, while cognitive proximity and social proximity significantly accelerate diffusion. Overall, the findings demonstrate how urban technological diversity drives knowledge recombination and how multiple forms of proximity structure the spatial diffusion of new technological combinations across Chinese cities.