Optimal Tax Policy, Market Imperfections, and Environmental Externalities in a Dynamic Optimizing Macro Model

This paper develops a dynamic real business cycle model that highlights pollution externalities (on welfare and production) and market imperfections and uses it to determine the socially optimal tax policy that encompasses labor income, capital income, and emission taxes. We show that the optimal tax on capital and labor income only addresses the production inefficiency (and is time‐invariant), while the tax on the environmental externalities affects both the production inefficiency and the environmental spillovers (and is time‐varying). More interestingly, the socially optimal emission tax will be characterized by a Keynesian‐like stabilizer that is designed to mitigate business cycle fluctuations, i.e., that will stimulate the economy with a lower emission tax during recessions. In a positive analysis, we show that the beneficial effects arising from pollution taxation will become larger the greater is the degree of the firms’ monopoly power. In addition, a triple dividend in terms of improving environmental quality and increasing employment and firms’ profit can be simultaneously realized if the environmental production externality is more significant and if the elasticity of intertemporal substitution in consumption is relatively small.