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Abstract The world has 1.4 billion passenger vehicles. How should governments regulate their air pollution emissions? A Pigouvian tax is technologically infeasible. Most countries instead rely on exhaust standards that limit air pollution emissions per mile for new vehicles. We assess the effectiveness and efficiency of these standards, which are the centerpiece of U.S. Clean Air Act regulation of transportation, and counterfactual policies. We show that the air pollution emissions per mile of new U.S. vehicles has fallen spectacularly, by over 99%, since standards began in 1967. Several research designs with a half century of data suggest that exhaust standards have caused most of this decline. Yet exhaust standards are not cost-effective in part because they fail to encourage scrap of older vehicles, which account for the majority of emissions. To study counterfactual policies, we develop an analytical and a quantitative model of the vehicle fleet. Analysis of these models suggests that tighter exhaust standards increase social welfare and increasing registration fees on dirty vehicles yields even larger gains by accelerating scrap, although both reforms have complex effects on inequality. 

Electric vehicle (EV) sales have been rapidly growing around the world, spurred by technology advances and policy actions. This study leverages rich data on all individual new light-duty vehicles sold in the United States from 2014 to 2020. We examine how EV attributes, prices, and sales have evolved, exploring substantial heterogeneity across geography, vehicle class, price range, and demographics. We use a matching analysis to compare EVs to similar conventional vehicles to find that EVs have been surprisingly competitive in very recent years. This suggests that constrained supply is an important determinant of the low overall EV market share.