Countries environmental performance assessment A. Zanella a* , A. S. Camanho. b , T. G. Dias c a Faculdade de Engenharia da Universidade do Porto, Porto, Portugal andreia.zanella@fe.up.pt b Faculdade de Engenharia da Universidade do Porto, Porto, Portugal acamanho@fe.up.pt c Faculdade de Engenharia da Universidade do Porto, Porto, Portugal tgalvao@fe.up.pt * Corresponding Author Abstract Environmental performance assessments are often conducted using environmental indicators. Although these indicators provide a starting point for performance assessments, they do not provide guidelines that countries should follow to improve performance. This paper develops an enhanced DEA model that provides a single summary measure of countries environmental performance, based on the aggregation of the indicators that underlie the estimation of the Environmental Performance Index (EPI). The main contribution of the methodology used in this paper is to enable benchmarking, such that it becomes possible to identify the strengths and weaknesses of each country, as well as the peers that inefficient countries should follow to learn the best environmental practices. Keywords: environmental performance, Data Envelopment Analysis, benchmarking 1- Introduction The environmental concerns have increased dramatically in the past few years and are now among the most serious challenges affecting people's well-being. Besides the climate change that has been widely discussed, other environmental problems such as local air and water pollution, soil erosion, water scarcity, deforestation, and loss of biodiversity are also becoming more serious [World Bank, 2008]. Countries are facing new challenges to control their waste production and to reduce the consumption of natural resources, in order to achieve the environmental targets