Government R&D and green technology spillovers: the Chernobyl disaster as a natural experiment

Using data on green patents filed at the European Patent Office from 1980 to 1984, this paper investigates the effect of increasing government R&D budget on green technology spillovers. Spillovers are measured with patent forward citations over the period 1981-1988. The level of government R&D budget is instrumented leveraging the unexpected occurrence of the Chernobyl nuclear accident-that exogenously pushed governments to reduce their energy-related R&D budgets-in a difference in differences setting. 2SLS results show that a 10% increase in government R&D increases by some 0.7% the number of citations received by green patents. Although positive and significant, the small magnitude of the estimated elasticity suggests that government R&D takes time to let innovation spillovers from green technologies to materialize with some relevance. Interestingly, increasing government R&D expenditures fosters green technology spillovers across traditional (non-green) fields and enlarges the technological breadth of inventions citing green patents. Overall, I conclude that government R&D fosters green knowledge spillovers, accelerates hybridization processes and favors technological diversification around green technologies. However, these positive effects seem to materialize at a slow pace.