This paper revisits the debate about the appropriate differential equation that governs the evolution of knowledge in models of endogenous growth. We argue that the assessment of the appropriateness of an equation of motion should not only be based on its implications for the future, but that it...

Climate mitigation policy should be imposed over a long period, and spur development of new technologies in order to make stabilization of green house gas concentrations economically feasible. The government may announce current and future policy packages that stimulate current R&D in...

Since governments can influence the demand for a new abatement technology through their environmental policy, they may be able to expropriate innovations in new abatement technology ex post. This suggests that incentives for environmental R&D may be lower than the incentives for market goods...