How much should governments subsidize the development of new clean technologies? We use patent citation data to investigate the relative intensity of knowledge spillovers in clean and dirty technologies in two technological fields: energy production and transportation. We introduce a new...

Policies on climate change that encourage 'clean innovation' while displacing 'dirty innovation' could have a positive impact on short-term economic growth while avoiding the potentially disastrous reduction in GDP that could result from climate change over the longer term.