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FAQs

General FAQs

What is the EPI?
How many countries does the EPI include?
Why were some countries not included in the EPI?
Who created the EPI?
Why the EPI?
Who uses the EPI? How do policymakers perceive the EPI? Where is it being applied in real-world contexts?
When will the EPI be released next?

Report + Data Citation

Can I download the data used to calculate the ESI and EPI? Where would I find this data?
Can I use the EPI data in my own academic report? What’s the proper citation?
Can I use the graphics, charts, and plots from the EPI website?
How do I properly cite data from a single indicator or dataset?

EPI Methods

What’s new for the 2014 EPI?
How do you determine what indicators are selected for the EPI?
Where do the data come from?
What criteria are used to determine whether a dataset is used in the EPI?
How can you verify the quality of the data used to construct the EPI?
How are the weightings determined? How did you assign weights to these scores?
How do I interpret the EPI or results?
(A) How do the ESI and EPI compare?
(B) How do the various iterations of the EPI compare?
(C) Can I compare the results over time?
​What kind of peer review process does the EPI undergo?

Design + Feedback

Who designed the EPI website?
Can I leave feedback for the EPI?

What is the EPI?

The Environmental Performance Index (EPI) ranks how well countries perform on high-priority environmental issues in two broad policy areas: protection of human health from environmental harm and protection of ecosystems. Within these two policy objectives the EPI scores country performance in nine issue areas comprised of 20 indicators. Indicators in the EPI measure how close countries are to meeting internationally established targets or, in the absence of agreed targets, how they compare to the range of observed countries.

How many countries does the EPI include?

The 2014 EPI includes 178 countries, or 99 percent of global population, 98 percent of land, and 97 percent of global GDP.

Why were some countries not included in the EPI?

Inclusion in the EPI requires countries have data for all of the indicators included in the Indicator Framework, unless an issue is considered ‘immaterial’ or not relevant for that particular indicator (e.g., a landlocked country does not have a coastline and would therefore not have a viable fisheries industry. See the 2014 EPI report for more details about Materiality Thresholds).  Therefore, countries were excluded because of insufficient data.

Who created the EPI?

The 2014 Environmental Performance Index is a joint project between the Yale Center for Environmental Law and Policy (YCELP) and the Center for International Earth Science Information Network (CIESIN) at Columbia University, in collaboration with the Samuel Family Foundation and the World Economic Forum.

Why the EPI?

The EPI gives decisionmakers access to important environmental data organized in a way that is easily understandable, useful, and drives productive competition. The EPI allows countries to compare their performance to neighbors and peers. With the inclusion of time series data, countries can also see how their own performance has changed over time.

Who uses the EPI? How do policymakers perceive the EPI? Where is it being applied in real-world contexts?

The target audience for the EPI includes policymakers and government officials, however many branches of academia, environmental research, and the general public may find the EPI useful. The EPI’s quantitative approach allows policymakers and other experts a comparative understanding of environmental performance relative to other countries.

Policymakers can benefit greatly from incorporating EPI results into their policy focus. Because environmental sustainability has emerged as a critical policy focus, there are increasing demands for explanations of performance in human health and environmental welfare. Many challenges arise from resource management strategies and the EPI’s data-driven and empirical approach allows easy identification of environmental performance problems.

EPI results are being applied in real-world contexts as many countries are making necessary policy adjustments towards improvement and long-term sustainability (See Indicators in Practice). Indicators are systematically and analytically tracked to allow policymakers to address relative environmental performance issues. Through identifying successful practices and optimal investments, top EPI performers can serve as models for improvements in environmental sustainability, law and governance, and regulatory regimes.

The EPI also reveals significant gaps in data, weaknesses in methodological consistency, and lack of systematic processes for verifying government-reported data. Policymakers may apply the EPI results to improve data collection, analysis, review, and verification toward future policy refinement and maximum return on government investments.

When will the EPI be released next?

The EPI is released biennially, with the next edition planned for 2016.

Can I download the data used to calculate the ESI and EPI? Where would I find this data?

All data and reports for all previous editions of the ESI and EPI can be found in our Previous Work section.

The 2014 EPI data and report are available in our Downloads section.

Can I use the graphics, charts, and plots from the EPI website?

You may use the graphics, charts, and plots from the EPI website with proper attribution:

Hsu, A., J. Emerson, M. Levy, A. de Sherbinin, L. Johnson, O. Malik, J. Schwartz, and M. Jaiteh. (2014). The 2014 Environmental Performance Index. New Haven, CT: Yale Center for Environmental Law and Policy. Available: http://www.epi.yale.edu.

Can I use the EPI data in my own academic report? What’s the proper citation?

We welcome the use of published EPI materials with proper attribution. Currently, all data for editions of the ESI and EPI are available to the public in our Downloads section.

Report Citation: Hsu, A., J. Emerson, M. Levy, A. de Sherbinin, L. Johnson, O. Malik, J. Schwartz, and M. Jaiteh. (2014). The 2014 Environmental Performance Index. New Haven, CT: Yale Center for Environmental Law and Policy. Available: http://www.epi.yale.edu.

How do I properly cite data from a single indicator or dataset?

Depending on how you plan to use the data, it may be appropriate to acknowledge the original data source or developer that provided data for an EPI indicator. In these cases, users can refer directly to the sources provided in the Issue Profiles, or the references provided in Indicator Metadata.

What’s new for the 2014 EPI?

The 2014 EPI report and the accompanying website offer several innovations and improvements over past versions of the Index, including:

New website. The new website gives users unparalleled access to the EPI scores, rankings, and data, allowing users to create their own peer group comparisons, to explore individual environmental issues in depth, to download all the data that underlie the 2014 EPI, and to access real-world stories that add nuance to the EPI.

New data and improved indicators. The 2014 EPI presents new Climate and Energy indicators that account for differing economic and development status across the world’s countries. The Air Quality and Forests issue areas include new indicators for Air Pollution and Change in Forest Cover that make use of cutting-edge satellite data for results that are more reflective of the actual state of the environment. For the first time anywhere, the 2014 EPI introduces a new indicator of Wastewater Treatment.

In addition, the 2014 EPI ranks 178 countries, more than ever before and includes more countries from sub-Saharan Africa and Small Island Developing States (SIDS) such as Palau and Kiribati.

How do you determine what indicators are selected for the EPI?

The EPI aims to cover environmental public health and ecosystem vitality through a measurable body of indicator information. We believe the indicators, assessed through a proximity-to-target approach, present the best data on the most relevant and pressing issues in environmental policy and resource management. Criteria from other important policy assessments are also incorporated into the EPI to offer a comprehensive assessment of current environmental health and ecological issue areas.

EPI indicators are carefully selected from extensive reviews of scientific literature and consultations with experts from each policy issue. Indicators are chosen to best gauge how close countries are to established environmental policy goals and correspond to long-term public health or ecosystem sustainability targets.

Once indicators are reviewed and agreed upon, candidate datasets are evaluated and compiled by the Yale University and Columbia University teams. The source of targets for each 2014 EPI indicator is found in the Indicator Metadata, and a summary of the EPI framework is found in our Methods section.

For details on the EPI development process, see Measuring Progress: A Guide from the Developers of the Environmental Performance Index (EPI)

Where do the data come from?

Descriptions of indicators included in each issue category are described in the issue profiles. Complete indicator metadata, which includes a description of the data sources, targets, and relevant statistical transformations, is available for download here.

What criteria are used to determine whether a dataset is used in the EPI?

We conduct a thorough expert review process to identify all potential datasets for measuring performance on high-priority environmental concerns.  Each dataset is then evaluated using the following criteria:

Relevance: The indicator tracks the environmental issue in a manner that is applicable to countries under a wide range of circumstances.

Performance orientation: The indicator provides empirical data on ambient conditions or on-the-ground results for the issue of concern, or is a “best available data” proxy for such outcome measures.

Established scientific methodology: The indicator is based on peer reviewed scientific data or data from the United Nations or other institutions charged with data collection.

Data quality: The data represent the best measure available. All potential data sets are reviewed for quality and verifiability. Those that do not meet baseline quality standards are discarded.

Time series availability: The data have been consistently measured across time, and there are ongoing efforts to continue consistent measurement in the future.

Completeness: The dataset needs to have adequate global and temporal coverage to be considered.

How can you verify the quality of the data used to construct the EPI?

The EPI relies on an expert network of dozens of scientists, policymakers, and other stakeholders from research organizations, academic institutions, government agencies, and intergovernmental organizations to peer review and develop indicators using the best available, global datasets. Collaboration and review from this extensive network ensures that each dataset used in the EPI represents the “best available,” although it may not be possible for the EPI team to individually corroborate datapoints reported by countries.

In some instances, steps are taken to fill data gaps and are clearly denoted in the Indicator Metadata.

To avoid conflict of interest, we do not accept any data submissions directly from countries. If there are any perceived discrepancies in the EPI data, please contact us. We are happy to put you in touch with a contact from the relevant data collection entity to ensure that the correct data are included in future versions of the EPI.

How are the weightings determined? How did you assign weights to these scores?

In the field of composite indices, the issues of weighting and aggregation are particularly sensitive and subjective. The expert community has no clear consensus on how to best determine a methodological strategy for combining diverse issues, such as those represented in the EPI. We assign explicit weights to the indicators, policy categories, and objectives to create the aggregate EPI score. The weightings we selected for the purposes of aggregation only represent one viewpoint. While our selection was reached with the help of collaborating experts, we recognize there may be legitimate differences of opinion regarding the relative importance of policy categories.

The two objectives in the EPI – Environmental Health and Ecosystem Vitality – are weighted roughly equally to achieve an approximate equal relationship between the overall EPI score and each objective score. Within each objective, policy issues are weighted based on quality and relevance of the data and indicator, according to expert judgment. A detailed description of processes for establishing indicator weights is discussed in the Methods section of the EPI report.

See the Measuring Progress manual for more information with respect to options for weighting in composite indices.

How do I interpret the EPI or results?

The results of the EPI aim to measure the efficacy (i.e., “performance”) of national environmental policies using datasets and indicators consistent for all countries at the national level. Through a proximity-to-target approach, it becomes possible to gauge a country’s achievement towards policy targets.

The overall rankings of the EPI are meant to be used only as an indicative value. It is incorrect to say a lower score means a policy is “less strict.” Rather, a lower score indicates a country may be further from achieving a predefined indicator target. The proximity-to-target measurement is defined as a numerical value based on a range of 1-100. If an indicator target is met, that country will receive a score of 100. In some cases, no country receives a score of 100 (in the case of the Climate and Energy and Fisheries policy issues). Overall, the scores are weighted as a percentage of 100 to determine a country’s overall EPI score.

How do the ESI and EPI compare? 

The Environmental Sustainability Index (ESI) was the predecessor to the Environmental Performance Index (EPI). The ESI was a first attempt to rank countries on 76 different elements of environmental sustainability, including natural resource endowments, past and present pollution levels, environmental management efforts, contributions to the protection of the global commons, and a society’s capacity to improve environmental performance over time. There are four iterations of the ESI – the 2000, 2001, 2002, and 2005 versions. 

How do the various iterations of the EPI compare?

The 2006 Pilot, 2008, 2010, 2012, and 2014 EPIs are focused on environmental performance, rather than sustainability measures. The datasets used to construct the EPI reports may vary slightly year to year. The 2006 EPI is a pilot version and includes only a subsection of environmental performance indicators. The structures and contents of the EPIs have changed over time due to methodological refinements, management trends, and policy changes.

Can I compare the results over time?

No. Due to changes in the structures, data, and methodologies of the EPI reports, rankings are not strictly comparable in that a particular standing in one year and another ranking in a subsequent edition do not indicate a change in performance. The inability to truly compare rankings between versions of the ESI and EPI are due to changes in data sources, imputations, methodology, framework, target setting, weighting, and aggregation. For year-to-year comparisons, we recommend use of the ‘back-casted’ EPI scores, which are available in the Country Profiles section.

What kind of peer review process does the EPI undergo?

The EPI is produced by teams of expert contributors and research staff and draws upon 15 years of research and development. Extensive consultations are made with subject-area specialists, statisticians, and policymakers to gather policy-important issues, develop the indicator framework, and collect the underlying data. Although many datasets are based on reporting by national governments and are not subject to external review or verification, reviews of data-relevance and sources are performed throughout the entire EPI development.

Who designed the EPI website?

We worked with Matthew Schwartz Design Studio (MSDS) on the concept, design, and development of the EPI website. Yinan Song and Anne Householder, students at Yale University, designed and produced the EPI indicator infographics, the Summary for Policymakers, and the 2014 EPI Report.

Can I leave feedback for the EPI?

We welcome any feedback or suggestions. Contact us here.

 

Methods

The Environmental Performance Index (EPI) is constructed through the calculation and aggregation of 20 indicators reflecting national-level environmental data. These indicators are combined into nine issue categories, each of which fit under one of two overarching objectives. Click on "Learn More" to explore the complete methods.

Data Explorer

The EPI Data Explorer allows users to dynamically investigate global data: Compare environmental performance with GDP, population, land area, or other variables; create a chart that highlights all 178 ranked countries, only those in a specific region, or a custom-defined group. There's a lot more to the data than rankings, so dive in.