A correlation is presented between the UN human development index and per capita energy consumption for 120 nations. A strong relationship between index values and energy consumption is observed for the majority of the world. Additionally, a distinct secondary trend emerges from the dataset, representing heavy energy exporters such as the Organization of the Petroleum Exporting Countries and some Former Soviet Union nations, among others. The preliminary observation is made that these two trends closely resemble saturation curves, exhibited by a variety of natural phenomena. For the primary trend, three regions are isolated: a steep rise in human development relative to energy consumption for energy-poor nations; a moderate rise for transitioning nations; and essentially no rise in human development for energy-advantaged nations, consuming large amounts of modern energy. These correlations suggest that tremendous gains in human development are possible for the world's poorest, with small incremental access to energy. (c) 2007 Elsevier Ltd. All rights reserved.