Energy Indicators for Sustainable Development: Guidelines and Methodologies International Atomic Energy Agency United Nations Department of Economic and Social Affairs International Energy Agency Eurostat European Environment Agency

METHODOLOGICAL DESCRIPTION 
(a) Underlying Definitions and Concepts: Proven reserves indicate the resources in 
place that have been assessed as exploitable under present and expected economic 
conditions with available technology. 
(b) Measuring Methods: The estimates are based on the results of geological and 
exploratory information about an area or on evidence of the duplication or parallelism 
of geological conditions that occurs in known deposits. Unproven deposits are not 
included. The lifetime of proven fuel reserves in terms of the reserves-to-production 
ratio is computed by dividing the proven energy reserves of a commodity at the end of 
a year by the total production of that commodity in that year. 
(c) Limitations of the Indicator: The rate of use of energy reserves depends on 
many factors, including economic conditions, prices, technological progress and 
exploration efforts. Therefore, this indicator represents only a relative measure of 
reserve availability. For many countries, reserve-to-production ratios for oil and gas 
have been constant over many years, despite increasing exploitation of these 
resources. This is because when known reserves start to be depleted, greater effort 
typically is put into identifying new reserves as a replacement. Trends in reserve-to-
production ratios may therefore underestimate the total resource available, on the one 
hand, while providing inaccurate information about the extent to which a finite 
resource is being exhausted, on the other hand. 
(d) Alternative Definitions/Indicators: The total reserves and depletion rate are 
alternative measures for this indicator. 
ASSESSMENT OF DATA 
(a) Data Needed to Compile the Indicator: Data on available energy reserves and 
production. 
(b) National and International Data Availability: Data on proven fossil fuel 
reserves are available from the annual publication Survey of Energy Resources by the 
World Energy Council and are subject to frequent revision. Such data are also 
available from national and international oil and gas companies. Data on uranium 
reserves are available from joint publications of the International Atomic Energy 
Agency (IAEA) and the Nuclear Energy Agency (NEA). 
REFERENCES 
• BP. Statistical Review of World Energy. Published annually. London, UK: 
British Petroleum. 
• NEA/IAEA, various editions. Uranium: Resources, Production and Demand. 
Paris, France: Nuclear Energy Agency (NEA)/International Atomic Energy 
Agency (IAEA). 
• UNDP/UNDESA/WEC, 2000, World Energy Assessment. New York, USA: 
United Nations Development Programme. 
• UNSD, various editions. Energy Statistics Yearbook. Published annually. New 
York, USA: United Nations Statistics Division. 

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• USGS, various editions. World Petroleum Assessment. Washington DC, USA: 
United States Geological Survey. 
• WEC, various editions. Survey of Energy Resources. Published annually. 
London, UK: World Energy Council.