(February 2012, 97 pages, 4.03 MB PDF). The 2012 EPI ranks 132 countries, using 22 indicators in ten major policy categories including air and water pollution, climate change, biodiversity, and forest management. The EPI has been produced every two years since 2006 by researchers at CIESIN and Yale University’s Center for Environmental Law and Policy. For the first time, a complementary Pilot Trend Environmental Performance Index (Trend EPI) has also been produced. The Trend EPI shows country improvement from 2000 to 2010.