Score contribution per author:
α: calibrated so average coauthorship-adjusted count equals average raw count
For political and practical reasons, environmental regulations sometimes treat point-source polluters, such as power plants, differently from mobile-source polluters, such as vehicles. This paper measures the extent of this regulatory asymmetry in the case of nitrogen oxides (NO<sub>x</sub>), the most recalcitrant criteria air pollutant in the United States. We find significant differences in marginal abatement costs across source types: the marginal cost of reducing NO<sub>x</sub> from cars is less than half the marginal cost of reducing NO<sub>x</sub> from power plants. Our results measure the possible efficiency gains and distributional implications associated with increasing the sectoral scope of environmental regulations.(JEL Q53, Q58, R41)