(February 2010, 87 pages, 3.0 MB PDF). The Index, produced every two years since 2006 by researchers at CIESIN and Yale University’s Center for Environmental Law and Policy, is based on twenty-five indicators grouped within ten core policy categories—including environmental health, air quality, water resource management, biodiversity and habitat, forestry, fisheries, agriculture, and climate change—in the context of two objectives: environmental health and ecosystem vitality. The EPI’s proximity-to-target approach, in which each country’s performance is measured against clearly defined targets, enables comparisons among countries with very different characteristics.