The suggested citation for the 2026 EPI is …

Wendling, Z. A., Emerson, J. W., Esty, D. C., de Sherbinin, A., Block, S., et al. (2026). 2026 Environmental Performance Index. New Haven, CT: Yale Center for Environmental Law & Policy. https://epi.yale.edu

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 2026 EPI.

A country’s current score or rank in the 2026 EPI should not be compared to scores or ranks from previous versions of the Index. With every iteration of the EPI, we change methods and datasets to reflect the latest advances in science and metrics and to make our metrics more relevant to broad audiences. These changes mean that scores calculated under the old methods are not comparable to the new scores. Any apparent differences in scores or ranks could be driven more by methodological decisions than by changes in country performance.

To gauge how well a country performs over time, we recommend looking at individual country profiles in the 2026 EPI. They show how a country scores by applying our current methods to the most recent data and how those scores have changed over the past decade, when historical data are available.

Backcasting scores using the 2026 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, one would need to impute missing values for all the underlying indicators over a common period. Such missing data imputation 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 in the Technical Appendix.

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.

Older versions of the EPI can be downloaded via the dataverse service.

The EPI is released biennially in even-numbered years.

This website will be updated as the release of the next EPI draws closer.

No. The 2026 EPI is released under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. Neither the 2026 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.

Yes. The 2026 EPI is released under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License. You may use the 2026 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.

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.

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.

EPI data may contain missing values for one of two main 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.

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 the Methodology Chapter from the report. If you think that we missed an important and relevant dataset, please let us know at epi@yale.edu.

The suggested citations for previous versions of the EPI and the Environmental Sustainability Index (ESI) are

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

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.