Abstract: This paper studies the design of a carbon tax when environmental factors, such as air carbon-dioxide emissions (CO2), directly affect agents’ marginal utility of consumption. Our first result is that the optimal tax is determined by the shadow price of CO2 emissions. We then use asset-pricing theory to estimate this implicit price in the data and find that the optimal tax is pro-cyclical. It is therefore optimal to use the carbon tax to “cool down” the economy during booms and stimulate it in recessions. The optimal policy not only generates large welfare gains, it also reduces risk premiums and raises the average risk-free real rate. The effect of the tax on asset prices and welfare critically depends on the emission-abatement technology

Abstract: The first contribution of this paper is to develop a model that jointly accounts for the missing disinflation in the wake of the Great Recession and the subsequently observed inflation-less
recovery. The key mechanism works through heterogeneous expectations that may durably lose their anchorage to the central bank (CB)’s target and coordinate on particularly persistent below-target paths. We jointly estimate the structural and the learning parameters of the model by matching moments from both macroeconomic and Survey of Professional Forecasters data. The welfare cost associated with those dynamics may be reduced if the CB communicates to the agents its target or its own inflation forecasts, as communication helps anchor expectations at the target. However, the CB may lose its credibility whenever its announcements become decoupled from actual inflation, for instance in the face of large and unexpected shocks.

Abstract: We explore the role of public subsidies in mitigating the transition risk associated with a climate-neutral objective by 2060. We develop and estimate an environmental dynamic stochastic general equilibrium model for the world economy featuring an endogenous market structure for green products. We show that public subsidies, financed by a carbon tax, are an efficient instrument to promote firm entry into the abatement goods sector by fostering competition and lowering the selling price of such products. We estimate that the subsidy, optimally distributed between startups at 60% and existing companies at 40%, will save nearly $2.9 trillion in GDP each year by 2060.