Technological Spillover Effects of State Renewable Energy Policy: Evidence from Patent Counts

We examine the effect of in-state and out-of-state renewable energy policies on wind energy patenting. Using a semiparametric fixed-effects Tobit model, we regress patent counts on a series of policy variables within a state and a spatially weighted average for each of these policies implemented in other states. We develop a lower bound for the marginal effects and find important differences across policy types. For renewable portfolio standards, overall demand matters. Policies in other states increase innovation, but own-state policies do not. In contrast, for financial incentives such as tax incentives and subsidy policies, own-state policies induce innovation.