Since the 1973 world oil crisis, monitoring trends in energy efficiency at the economy-wide level has been an important component of energy strategy in many countries. To Support this effort, various energy efficiency-related indicators have been developed. We examine some classical indicators which are often found in national and international energy studies in the 1970s and 1980s. We then describe the recent developments in using the index decomposition analysis to give an economy-wide composite energy efficiency index based on a bottom-up approach. This composite index is superior to the classical indicators as an economy-wide energy efficiency measure and has lately been adopted by a growing number of countries for national energy efficiency trend monitoring. (c) 2005 Elsevier Ltd. All rights reserved.