Chapter 1. Introduction

The Logic of Environmental Metrics

Sustainable development has entered a new era of data-driven environmental policymaking. To meet the ambitious targets outlined in the United Nations 2015 Sustainable Development Goals (SDGs) and the Paris Climate Agreement, countries must integrate environmental performance metrics across a range of pollution control and natural resources policies. Data provide additional tools and abilities to policymakers, enabling success by gauging progress or backsliding, identifying best practices, and revealing insights into sustainability challenges that would otherwise remain hidden.

The 2018 Environmental Performance Index (EPI) scores 180 countries on 24 performance indicators across ten issue categories covering environmental health and ecosystem vitality. These metrics provide a gauge at a national scale of how close countries are to established environmental policy goals. Now in its 11th iteration, policymakers, scholars, non-governmental organizations, and the media have relied upon the biennial release of the EPI for policy insights and tracking of trends in sustainability. The EPI turns the latest advances in environmental science with worldwide datasets to form into a powerful summary of the state of sustainability around the world.

Data must be carefully organized and communicated to have a meaningful impact on the policy process. Debates about environmental challenges are often hampered by lack of problem definition, uncertainty about the nature of these challenges, and ill-defined solutions. Gathering data into the EPI helps to resolve these difficulties. The EPI serves as a communication tool for translating complex ideas into simpler, more useful forms. The single, 0–100 score for each country serves as a starting point for deeper discussions. We invite government officials, non-governmental organizations, and citizens all over the world to analyze the sub-scores of the EPI to discern which issues are holding back sustainability. Country scores on the EPI are translated into rankings. The EPI rankings are intended to inspire countries to engage in healthy competition, vying to rise to the top of their peer groups. Backcasting EPI scores from historic data allows countries to track their progress over time. In these ways, the EPI offers several insights that are useful for identifying best practices, informing policy agendas, and setting priorities in environmental governance.

The 2018 Environmental Performance Index

The 2018 EPI represents a composite index. We begin by gathering data on 24 individual metrics of environmental performance, as shown in Figure 1-1. These metrics are aggregated into a hierarchy beginning with ten issue categories: Air Quality, Water & Sanitation, Heavy Metals, Biodiversity & Habitat, Forests, Fisheries, Climate & Energy, Air Pollution, Water Resources, and Agriculture. These issue categories are then combined into two policy objectives – Environmental Health and Ecosystem Vitality – and then finally consolidated into the overall EPI. To allow for meaningful comparisons, we construct scores for each of the 24 indicators, placing them onto a common scale where 0 indicates worst performance and 100 indicates best performance. How far a country is from achieving international targets of sustainability determines its placement on this scale. The indicator scores are then multiplied by weights, shown in Figure 1-1, and added together to produce scores at the levels of the issue categories, policy objectives, and the final EPI. These scores serve as the basis for country ranks. Indicators are constructed from the most recently available data for each of the 24 metrics of environmental performance. To track changes over time, we also apply the same methods to historic data in order to show what the EPI score for each country would be in a baseline year, generally ten years prior to the current report. We take the performance of every country and aggregate those data into measurements of global performance. We score these global aggregates on the same 0–100 scale as individual countries, showing the state of the world on each indicator. The results of the 2018 EPI – the scores, rankings, trends, and global aggregates – translate environmental data into terms that are comprehensive and comprehendible.

Report Organization

This report provides comprehensive coverage of the 2018 Environmental Performance Index. It proceeds in several sections. Chapter 2 discusses the methodology of the 2018 EPI. Chapter 3 summarizes the results, highlighting key findings of the EPI, global performance, country performance, and trends among peer groups. Chapter 4 is a retrospective on the 20-year history of the EPI, offering lessons learned from producing a composite index of environmental performance and noting our impact. Chapters 5–14 give background information on each of the issue categories in greater detail, explanations of the indicators, and discussions of the results. Further details about the 2018 EPI are available on our website,, including data downloads, country profiles, and the Technical Appendix.