Optimal combination of innovation and environmental policies under technology licensing

Under what conditions will a carbon tax encourage environmental innovation? Can a regulator design an optimal environmental policy to reduce emissions and to promote clean technologies? This paper studies optimal environmental policy in the situation where a monopoly innovator develops and licenses dean production technologies to downstream polluting firms. We find that (i) a higher emission tax will encourage innovation when the burden of the tax payment in the polluters' costs and/or the price-elasticity of the demand for polluting goods are small, (ii) the innovation-inducing effects of emission tax are inversely related to the emission-reduction (Pigouvian) effects of the tax, and (iii) the social optimum can be achieved by the mix of tax and subsidy. We also show that if the policy instrument is limited to the tax, the second-best tax rate would lie between the marginal damage and the first-best rate. By performing numerical simulations, we also demonstrate that the optimal mix of the emission tax and R & D subsidy can have double dividend benefits.