Fraas and Lutter raise two important points in their comment on Muller and Mendelsohn (2009): How to design policies for sources that yield negative marginal damages? How does statistical uncertainty in the marginal damages affect the trading ratios across emitters? We address both issues in this response. JEL: H53, Q53, Q58

This paper argues for efficient environmental regulations that equate the marginal damage of pollution to marginal abatement costs across space. The paper estimates the source-specific marginal damages of air pollution and calculates the welfare gain from making the current sulfur dioxide allowance trading program for power plants more efficient. The savings from using trading ratios based on marginal damages are between $310 and $940 million per year. The potential savings from setting aggregate emissions efficiently and from including more sources of air pollution are many times higher.

This study presents a framework to include environmental externalities into a system of national accounts. The paper estimates the air pollution damages for each industry in the United States. An integrated-assessment model quantifies the marginal damages of air pollution emissions for the US which are multiplied times the quantity of emissions by industry to compute gross damages. Solid waste combustion, sewage treatment, stone quarrying, marinas, and oil and coal-fired power plants have air pollution damages larger than their value added. The largest industrial contributor to external costs is coal-fired electric generation, whose damages range from 0.8 to 5.6 times value added.