The Environmental Policy Uncertainty (EPU) Index measures changes in uncertainty surrounding environmental policy in the United States by analyzing more than 300 million newspaper articles published since January 1985. Using the NewsBank news aggregator, which includes approximately 15,000 local, regional, and national U.S. newspapers, the index tracks how frequently environmental policy uncertainty is discussed over time.
The methodology begins by identifying articles related to general economic policy uncertainty. To qualify, an article must include terms associated with the economy (such as economic or economy), uncertainty (such as uncertain or uncertainty), and at least one policy-related term, including Congress, Federal Reserve, legislation, regulation, White House, or deficit.
From this group of articles, those specifically addressing environmental policy are identified using a set of 31 environmental keywords. An article is included in the Environmental Policy Uncertainty Index only if it meets the general economic policy uncertainty criteria and contains at least one environmental keyword. These terms represent five major areas of environmental policy commonly discussed in academic literature: air and water pollution, climate change, non-renewable energy, renewable energy, and biodiversity and habitat conservation.
To construct the index, the monthly number of qualifying articles is divided by the total number of newspaper articles published during the same month. These monthly values are then normalized relative to the 1985–2009 average, creating a standardized time series that allows for meaningful comparisons over time. For example, an index value of 198 in January 2017 indicates that environmental policy uncertainty was discussed in newspapers at a rate 1.98 times the average observed between 1985 and 2009.
For additional details on the methodology and data, see Palikhe, Schaur, and Sims (2024).