EPI FAQ
How should I cite the EPI?
The suggested citation for the 2024 EPI:
Block, S., Emerson, J. W., Esty, D. C., de Sherbinin, A., Wendling, Z. A., et al. (2024). 2024 Environmental Performance Index. New Haven, CT: Yale Center for Environmental Law & Policy. https://epi.yale.edu
Where do data for the EPI come from?
Data for the EPI come from international organizations, research institutions, academia, and government agencies. Most of our data are verified by a third party or produced from a data collection process that can be accessed and audited by a third party to confirm results. Generally, we do not accept data directly from governments themselves. Our Technical Appendix provides additional details on data sources for all variables used in the 2024 EPI.
Why did a country rise/drop since the last EPI?
A country’s current score in the 2024 EPI should not be compared to scores from previous versions of the Index. With every version of the EPI, we change the methodology and use new datasets to reflect the latest advances in science and metrics. These changes mean that scores calculated under the old methods are not comparable to the new scores.
To gauge how well a country performs over time, we recommend looking at individual country profiles. They show how a country scores using the most recent data and how those scores have changed over the past decade.
Why don’t you backcast EPI scores?
Backcasting scores using the 2024 EPI methodology can be problematic for several reasons. As shown in our Technical Appendix, the underlying data series we use are asynchronous. Datasets have different beginning and end periods, some have several gaps in temporal coverage, and some have only a single year of observations. To produce a time series of the EPI, we need to impute missing values for all the underlying indicators over a common period, which can make it seem as if environmental performance was unresponsive to policy.
For researchers interested in time series analysis, we recommend working with individual indicators for which longitudinal observations are available, rather than aggregated scores.
To give some reference for how performance changes over time, we also backcast a score using data approximately ten years prior to the most recent data, if available. We sometimes referred to these ten-year backcasts as the “baseline” scores. The scores based on the most recent year for which data are available are sometimes referred to as the “current” scores. For simplicity, we most often discuss the differences between the current and baseline scores as the ten-year change in performance. We describe further details about temporal coverage and backcasting in the online Technical Appendix.
Can I assemble the releases of the EPI into a time series or panel dataset?
No. Because the underlying methodology and data change between versions of the EPI, it is not appropriate to assemble the scores from each release into a time series. If you wish to analyze longitudinal data on environmental performance, historic time series for many indicators are available on our downloads page.
Where can I find previous versions of the EPI?
Older versions of the EPI can be downloaded from the Socioeconomic Data and Applications Center (SEDAC).
Where is the EPI from 2023/2021/2019/2017/2015/etc. ?
The EPI is released biennially in even-numbered years.
When will the next EPI be released?
The next EPI will be released in 2026. This website will be updated as the release draws closer.
Can I use the EPI for commercial purposes?
No. The 2024 EPI is released under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Neither the 2024 EPI nor the data available on our downloads page may be used for commercial purposes. Our partners share data with us under certain restrictions, and the data usage agreements under which we operate prohibit the use of the EPI or derivative works in commercial products. Our data partners are listed in the data sources section of the Technical Appendix.
Can I use the EPI for educational, research, and other non-commercial purposes?
Yes. The 2024 EPI is released under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. You may use the 2024 EPI, including the scores, report, policymakers’ summary, and other material on this website, according to the terms of this license. Please email us at epi@yale.edu if you would like to reproduce specific images.
How recent are the data from which the EPI is calculated?
The EPI always attempts to use the most recent data available for each indicator. Some data are more recent than others, and some data systems take several years to collect data on every country. The most recent year for each indicator is reported in the Technical Appendix.
What can a country do to improve its score in the EPI?
Specific policy recommendations are beyond the scope of our analysis. EPI rankings and scores allow for meaningful comparisons across peer countries. We encourage countries that aspire to become more sustainable to look to peer leaders for insights, lessons, and best practices that might be most appropriate for their own, individual challenges.
We do make three general policy recommendations: every country should improve data collection on environmental outcomes, support global data systems, and incorporate metrics and rigorous analysis into policymaking processes.
Why is there a missing score in the data?
EPI data may contain missing values for one of two reasons. First, while the EPI strives to find datasets that are comprehensive, not all data are available for every country. Second, sometimes a metric will be judged as immaterial in the calculation of the EPI, e.g., landlocked countries will not have scores for fisheries or marine protected areas. To learn more about country coverage and materiality, please see our Technical Appendix.
Why didn’t you use a certain dataset?
While there are more data available now than ever before, not all datasets are applicable to the EPI. For a description of our data selection process, please see Chapter 14 on Methodology in the report. If you think that we missed an important and relevant data, please let us know at epi@yale.edu.
How should I cite previous versions of the EPI?
The suggested citations for previous versions of the EPI and the Environmental Sustainability Index (ESI) are
Wolf, M. J., Emerson, J. W., Esty, D. C., de Sherbinin, A., Wendling, Z. A., et al. (2022). 2022 Environmental Performance Index. New Haven, CT: Yale Center for Environmental Law & Policy. https://epi.yale.edu
Wendling, Z. A., Emerson, J. W., de Sherbinin, A., Esty, D. C., et al. (2020). 2020 Environmental Performance Index. New Haven, CT: Yale Center for Environmental Law & Policy. https://epi.yale.edu/
Wendling, Z. A., Emerson, J. W., Esty, D. C., Levy, M. A., de Sherbinin, A., et al. (2018). 2018 Environmental Performance Index. New Haven, CT: Yale Center for Environmental Law & Policy. https://epi.yale.edu/
Hsu, A., Esty, D. C., de Sherbinin, A., Levy, M. A., et al. (2016). 2016 Environmental Performance Index: Global Metrics for the Environment. New Haven, CT: Yale Center for Environmental Law & Policy.
Hsu, A., Emerson, J. W., Levy, M. A., de Sherbinin, A., Johnson, L., Malik, O. A., Schwartz, J. D., & Jaiteh, M. (2014). 2014 Environmental Performance Index. New Haven, CT: Yale Center for Environmental Law & Policy.
Emerson, J. W., Hsu, A., Levy, M. A., de Sherbinin, A., Mara, V., Esty, D. C., & Jaiteh, M. (2012). 2012 Environmental Performance Index and Pilot Trend Environmental Performance Index. New Haven, CT: Yale Center for Environmental Law & Policy.
Emerson, J. W., Esty, D. C., Levy, M. A., Kim, C. H., Mara, V., de Sherbinin, A., & Srebotnjak, T. (2010). 2010 Environmental Performance Index. New Haven, CT: Yale Center for Environmental Law & Policy.
Esty, D. C., Levy, M. A., Kim, C. H., de Sherbinin, A., Srebotnjak, T., & Mara, V. (2008). 2008 Environmental Performance Index. New Haven, CT: Yale Center for Environmental Law & Policy.
Esty, D. C., Levy, M. A., Srebotnjak, T., de Sherbinin, A., Kim, C. H., & Anderson, B. (2006). Pilot 2006 Environmental Performance Index. New Haven, CT: Yale Center for Environmental Law & Policy.
Esty, D. C., Levy, M. A., Srebotnjak, T., & de Sherbinin, A. (2005). 2005 Environmental Sustainability Index: Benchmarking National Environmental Stewardship. New Haven, CT: Yale Center for Environmental Law & Policy.
Esty, D. C., Levy, M. A., Granoff, I. M. E., & de Sherbinin, A. (2002). 2002 Environmental Sustainability Index. New Haven, CT: Yale Center for Environmental Law & Policy.
Esty, D. C. (2001). Toward data-driven environmentalism: the environmental sustainability index. Environmental Law Reporter News and Analysis, 31(5), 10603.
Esty, D. C., Levy, M. A., Granoff, I. M. E., & de Sherbinin, A. (2000). Pilot Environmental Sustainability Index. New Haven, CT: Yale Center for Environmental Law & Policy.
How is the EPI funded?
The EPI is funded through the generous support of the McCall MacBain Foundation.