Public R&D and green knowledge diffusion:\r\nEvidence from patent citation data

The present paper investigates the relationship between public R&D and the diffusion of green knowledge. To do so, we exploit information contained in green patents filed at the European Patent Office from 1980 to 1984. The diffusion of green knowledge is measured by meaning of patent citations. The level of public R&D is instrumented through the policy reaction to the 1986 Chernobyl nuclear accident – that affected the level of public R&D in the energy generation domain – in a difference in differences setting. Results show that a 10% increase in public R&D increases by around 0.7% the number of citations to green patents. Moreover, increasing public R&D fosters the diffusion of green knowledge across traditional (non-green) domains and increases the average technological distance of inventions citing green patents. This evidence suggests that public R&D is a driver of green knowledge diffusion, accelerates the hybridization of traditional innovation processes and fosters technological diversification.