Willingness to pay for air quality is a function of health and the costly defensive investments that contribute to health, but there is little research assessing the empirical importance of defensive investments. The setting for this paper is a large U.S. emissions cap and trade market – the NOx Budget Trading Program (NBP) – that has greatly reduced NOx emissions since its initiation in 2003. Using rich quasi-experimental variation, we find that the reductions in NOx emissions decreased the number of summer days with high ozone levels by about 25%. The NBP also led to reductions in expenditures on prescription pharmaceutical expenditures of about 1.9%. Additionally, the summer mortality rate declined by approximately 0.5%, indicating that there were about 2,200 fewer premature deaths per summer, mainly among individuals 75 and older. The monetized value of the reductions in pharmaceutical purchases and mortality rates are each roughly $900 million annually, suggesting that defensive investments are a significant portion of willingness to pay for air quality. Finally, we cautiously conclude that the reductions in ozone are the primary channel for these reductions in defensive investments and mortality rates, which indicates that willingness to pay for ozone reductions is larger than previously understood.

Areas of Focus: Climate Change
Definition
Climate Change
Climate change is an urgent global challenge. EPIC research is helping to assess its impacts, quantify its costs, and identify an efficient set of policies to reduce emissions and adapt...
Climate Economics
Definition
Climate Economics
Climate change will affect every sector of the economy, both locally and globally. EPIC research is quantifying these effects to help guide policymakers, businesses, and individuals working to mitigate and...
Climate Law & Policy
Definition
Climate Law & Policy
As countries around the world implement policies to confront climate change, EPIC research is calculating which policies will have the most impact for the least cost.
Environment
Definition
Environment
Producing and using energy damages people’s health and the environment. EPIC research is quantifying the social costs of energy choices and uncovering policies that help protect health while facilitating growth.
Air Pollution
Definition
Air Pollution
Air pollution from fossil fuel combustion poses a grave threat to human health worldwide. EPIC research is using real-world data to calculate the effects of air pollution on human health...