Comparison of EPA and Other Estimates of Mobile Source Rule Costs to Actual Price Changes

The Clean Air Act Amendments of 1990 stimulated a substantial number of new regulations for highway vehicles and their fuels. Among the issues of contention in many of those rules was the cost likely to result from new standards. EPA estimates of the expected cost of new rules were generally significantly lower than estimates by other stakeholders. To help assess the accuracy of various estimates, this study develops a comparison of ex ante cost estimates with actual ex post price changes. The general pattern that is revealed indicates that all ex ante estimates tended to exceed actual price impacts, with the EPA estimates exceeding actual prices by the smallest amount.