Energy intensities reflect not only energy efficiency but also changes in other effects such as weather and extent of occupancy. However, the advantage of considering individual energy intensities is that you may easily measure and track them over time. Measuring energy efficiency in the overall economy is more complex than in the individual sectors. The participant discussions in this session suggested EIA has opened Pandora's box. Participants seem well aware of the difficulties and complexities of doing energy-efficiency assessments for entire economy.
Different answers call for different indicators.
Definition Depends on Perspective. Definitional issues come down to whether one assumes a service perspective or a mechanistic, strict intensity, perspective with regard to energy efficiency. Measurement Depends on Policy Issues. Measurement of energy efficiency always relates to the specific policy issues at stake. As an example, from the global-warming perspective, the absolute carbon emissions are obviously most important.