Looking Back at Fifty Years of the Clean Air Act

After major expansion in 1970, the Clean Air Act led to substantial emissions reductions and health improvements—as well as some unintended consequences.



Jan. 6, 2020


Working Paper

Reading time

1 minute


Since 1970, transportation, power generation, and manufacturing have dramatically transformed as air pollutant emissions fell significantly. To evaluate the causal impacts of the Clean Air Act on these changes, we synthesize and review retrospective analyses of air quality regulations. The geographic heterogeneity in regulatory stringency common to many regulations has important implications for emissions, public health, compliance costs, and employment. Cap-and-trade programs have delivered greater emission reductions at lower cost than conventional regulatory mandates, but policy practice has fallen short of the cost-effective ideal. Implementing regulations in imperfectly competitive markets have also influenced the Clean Air Act’s benefits and costs.

Key Findings

  1. Spatially varying regulations can impose substantial costs on local economies.
  2. Current applications of market-based mechanisms may fall short of cost-saving expectations.
  3. Varying fuel content regulations across the United States may impose unnecessary costs on consumers in separated markets.
  4. Regulatory flexibility for fuel content rules doesn’t always yield cost-effective results.
  5. Unanticipated costs arising from overly optimistic technology projections are an important issue in the design of renewable fuel requirements.


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