[en] Improved energy efficiency is a key policy goal of all International Energy Agency (IEA) member countries, but tracking energy efficiency gains is not straightforward. As part of its contribution to the G8 Gleneagles Plan of Action, the IEA has been developing in-depth indicators-tools that provide data and analysis of energy use and efficiency trends. This paper gives an overview of the IEA indicator methodology and presents examples of how disaggregated indicators can be used to identify the factors that drive and restrain energy demand at the end-use level. A decomposition approach is also used to separate efficiency effects from the impacts of structure and activity. The results clearly show the important role that energy efficiency has played in shaping trends in final energy use in IEA countries for more than 30 years. However, the analysis also reveals that recent gains in energy efficiency have been much lower than in earlier decades. Accelerating energy efficiency improvements is therefore a crucial challenge for IEA governments and indicators have an important role to play in helping to develop and evaluate the policies that will be required.