First released as an Environmental Sustainability Index at the World Economic Forum in 2000, the Environmental Performance Index (EPI) emerged from an interdisciplinary team of researchers who believed that a data-driven approach to environmental policymaking would make it easier to spot problems, track trends, benchmark performance, highlight leaders and laggards, spotlight policy successes and failures, and identify best practices. Led by scholars at Yale and Columbia universities, the EPI ranks about 180 countries for which there are sufficient data on a series of performance indicators across a dozen environmental policy categories covering both environmental public health and ecosystem vitality – using a “proximity-to-target” methodology that tracks how close individual countries and the global community are to established environmental policy goals. Released on a biannual basis, the EPI has undergone continuous revision and refinement to reflect new learning and improved data, track trends over time, and provide a regularly updated performance scorecard. The policy impact of the EPI has been far-reaching. Dozens of nations have used the EPI to rethink their approach to policy and scholars across the world use the data in their analyses. More fundamentally, the EPI has helped to spark a trend toward more data-driven and empirical environmental policymaking including the world community’s commitment to the 2015 Sustainable Development Goals.