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FAQ

General:

Methodology:

Website:

General:

When will the EPI and Pilot Trend EPI be released next?

  • The EPI is released biennially, with the next edition in 2014. The Pilot Trend EPI will be released again once available data has been updated sufficiently to allow for new analysis.

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 on our website: http://epi.yale.edu.
  • The suggested citation for use of the 2012 materials:Emerson, J.W., A. Hsu, M.A. Levy, A. de Sherbinin, V. Mara, D.C. Esty, and M. Jaiteh. 2012. 2012 Environmental Performance Index and Pilot Trend Environmental Performance Index. New Haven: Yale Center for Environmental Law and Policy.

How do I interpret the EPI or results?

  • The results of the EPI aim to measure the policy efficacy (i.e. “performance”) of environmental performance by defining appropriate metrics and methodologies. Through a proximity-to-target approach, it becomes possible to gauge a country’s achievement towards policy targets through scientific evidence and best practices.
  • 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. Overall, the scores are weighted as a percentage of 100 to determine a country’s overall EPI score.
  • EPI results and analyses are described in Chapter 3 of the 2012 EPI report. Indicator targets are found in Appendix 1 of the 2012 EPI report.

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 and environmental research may find the EPI report 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 Case Studies). 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 Country Profiles on the 2012 EPI site (http://epi.yale.edu/epi2012/countryprofiles) list performance neighbors for each country, in terms of EPI performance levels and trends. The comparison of countries facing similar environmental dilemmas allows a better understanding of successful policy efforts.
  • 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. Through the goals of the 2012 EPI, time-series indicator data allow policymakers to track their progress towards well-established policy targets.

Methodology:

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 the country does not a materiality threshold for that particular indicator (e.g. a landlocked country does not have a coastline and would therefore not have a viable fisheries industry).  Therefore, countries were excluded because of insufficient data. A complete list of countries not included in the EPI is included in Appendix 3 (forthcoming). Data for those missing countries that are available are included in the full data spreadsheets.

(A) How do the ESI and EPI compare? (B) How do the Pilot 2006 and 2008/2010/2012 EPIs compare? (C) Can I compare the results over time?

  • (A) - 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. (http://epi.yale.edu/about/previouswork)
  • (B) - The 2006 Pilot, 2008, 2010, and 2012 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. Comparisons of ESI and EPI are discussed in Appendix 3 (forthcoming).
  • (C) - 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. 
  • The 2012 EPI does represent a shift in methodology towards trend—rather than snapshot—data. While 2012 EPI scores still cannot be directly compared to 2008 or 2010 scores, the 2012 Trend EPI attempts to fulfill the desire for an indication of performance changes over time by establishing the Pilot Trend EPI.

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

  • The 2012 EPI aims to cover environmental public health and ecosystem vitality through a measurable body of indicator information. We believe the 22 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 category. 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, the best available data are obtained through various international organizations and research groups. Candidate data sets are evaluated and compiled by the Yale University and Columbia University teams.
  • The source of targets for each 2012 EPI indicator is found in the Indicator Metadata  (http://epi.yale.edu/downloads). A summary of the EPI framework is found in Chapter 2 of the 2012 EPI report. Full descriptions of indicator selections and construction are found in Section 2.2 and Section 2.3 of the report.

What criteria are used to determine whether a dataset is used?

  • For the 2012 EPI, a thorough expert review process was conducted to identify all possible datasets that could be used to measure performance on pressing environmental concerns.  Each dataset was 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.

Where does the data come from?

  • Alliance for Zero Extinction
  • Anderson, K. (ed.), Distortions to Agricultural Incentives: A Global Perspective, 1955 to 2007, London: Palgrave Macmillan and Washington DC: World Bank, October 2009.
  • Battelle Memorial Institute, van Donkelaar, A., R. V. Martin, M. Brauer, R. Kahn, R. Levy, C. Verduzco, and P. J. Villeneuve. 2010. Global Estimates of Exposure to Fine Particulate Matter Concentrations from Satellite-based Aerosol Optical Depth, Environ. Health Perspectives, 118(6).
  • Döll, P., K. Fiedler, and J. Zhang. Global-scale analysis of river flow alterations due to water withdrawals and reservoirs, Hydrol. Earth Syst. Sci., 13, 2413–2432, 2009
  • FAO, Global Forest Resources Assessment 2010
  • International Energy Agency (IEA)
  • IUCN and UNEP-WCMC (2011) The World Database on Protected Areas (WDPA): January 2011. Cambridge, UK: UNEP-WCMC.
  • Nominal rate of assistance to the agriculture sector
  • Sea Around Us Project, University of British Columbia Fisheries Centre
  • Smith, S.J.,  J. van Aardenne, Z. Klimont, R.J. Andres4, A. Volke, and S. Delgado Arias. (2011). Anthropogenic sulfur dioxide emissions: 1850–2005, Atmos. Chem. Phys., 11, 1101–1116. Population data from the World Development Indicators, The World Bank.
  • Smith, S.J.,  J. van Aardenne, Z. Klimont, R.J. Andres4, A. Volke, and S. Delgado Arias. (2011). Anthropogenic sulfur dioxide emissions: 1850–2005, Atmos. Chem. Phys., 11, 1101–1116.GDP data in PPP from the World Development Indicators, The World Bank.
  • UNEP Chemicals, "Master List of Actions on the Reduction and/or Elimination of the Releases of Persistent Organic Pollutants, Fifth edition", June 2003
  • UNEP World Conservation Monitoring Centre
  • United Nations, Department of Economic and Social Affairs, Population Division
  • University of Maryland
  • World Health Organization
  • World Health Organization / UNICEF Joint Monitoring Programme (JMP) for Water Supply and Sanitation

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

  • The EPI builds on the best data available from research organizations, academic institutions, government agencies, or global organizations. Many data sets are based on reporting by national governments and unfortunately are not subject to any external review or verification.
  • Although the EPI uses the best data available, data constraints and methodology limitations make the EPI a work in progress. A wide range of data is compiled through various international, academic, and research institutes but consistent time-series data related to important policy indicators are poorly available. In some instances, steps are taken to fill data gaps and are clearly denoted in the Indicator Metadata, which can be downloaded from here (http://epi.yale.edu/sites/default/files/downloads/appendix01_indicator-profiles.pdf).
  • The 2012 EPI contains the most current data available. Future EPI releases will contain updated data sets as they become available. Our long-term goal is to build indicators on in situ data or direct observations to best track on-the-ground environmental results. The 2012 EPI includes two indicators (Forest Loss and PM 2.5) that are derived from satellite data.
  • A complete review of 2012 EPI data including gaps and deficiencies is found in the 2012 EPI report. A preliminary sensitivity analysis for the 2012 EPI is also available for download: http://epi.yale.edu/downloads.

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. There is no clear consensus among the expert community on composite index construction as to 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 in order to create the aggregate EPI score (see Figure 2.1 in the EPI Report). 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 main objectives of the EPI framework are the Environmental Health Objective, which contributes 30% of overall weighting, and the Ecosystem Vitality Objective, which contributes 70% of overall weighting. These relative contributions do not reflect the prioritization of “nature” indicators over those of environmental health, but rather accomplish a balance between the contribution of these policy objectives to the overall EPI, and also recognize that humans require healthy ecosystems just as much as they require clean air and potable water. The change in weightings simply reflects a much-needed statistical correction to the aggregation method to produce EPI scores more balanced between the two objectives. Figure 2.3 in the Full Report demonstrates the balance achieved through these weights.
  • Within each objective, policy categories are weighted based on quality of the data and indicator, according to expert judgment. Indicator weights are shown in Figure 2.1 of the 2012 EPI report (below). A detailed description of processes for establishing indicator weights is discussed in Section 2.4. For an interactive chart of EPI metrics, please visit: http://epi.yale.edu/Metrics.

How is the Pilot Trend EPI (Trend EPI) calculated?

  • The Pilot Trend EPI (Trend EPI) is based on the same Indicator Framework as the 2012 EPI. However, instead of just calculating proximity-to-target scores using the most recent year of data available, the Trend EPI takes advantage of historical data to measure performance from roughly 2000 to 2010.  In some cases, data for a particular indicator may only be available up until year 2005 or 2009 (see Indicator Metadata). In other cases, a time series is not available, such as the Water Resources indicator. In other cases, the indicators themselves are change variables (e.g. Forest Loss) and could be used directly. For each indicator with a meaningful time series, we use a simple linear regression model to determine a rate of improvement or decline for a particular indicator or level of aggregation (i.e. policy category, objective, or the EPI index). This number is then translated to a score from -50 to 50, where 0 represents no change. The extremes (50 is the “best” improvement and -50 represents a “biggest decline”) are based on the observed trend results, indicator by indicator. For the few indicators that are already change indicators (Forest Loss, Forest Growing Stock, Forest Cover, and Change in Water Quantity), the trend scores range from -50 to 0.
  • Aggregation from the individual indicator to the policy categories and objectives proceeds using the same methodology and weights as the 2012 EPI. Aggregation of the policy objectives to create the Pilot Trend EPI uses different weights, however, to help maintain a balance between trend performances on Environmental Health and Ecosystem Vitality.

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 ten years of research and numerous reports. 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.
  • As new methodologies evolve, the EPI will reflect these changes. The commitment of experts from around the world allow for continuous reviews of the index. For more information on the overall development of the EPI, see Chapter 2 of the 2012 EPI report.

Website

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

How were the countries of similar performance determined for the Country Profiles?

  • Countries of similar performance and trend performance were identified through a k-nearest-neighbor analysis of policy category performance and trend results.

Can I leave feedback for the EPI?