Definition:
Energy consumption per GDP is the amount of primary energy used per unit of income generated by a country's economy. All primary sources of energy, including coal and coal products, oil and petroleum products, natural gas, nuclear, hydroelectric, etc. are included here. Data are reported in tonnes (metric tons) of oil equivalent (toe) per million constant 2000 international dollars.

Consumption equals indigenous production + imports - exports - energy delivered to international marine bunkers +/- stock changes. The International Energy Agency (IEA) refers to these data as Total Primary Energy Supply (TPES). Energy losses from transportation, friction, heat, and other inefficiencies are included in these totals.

Gross Domestic Product (GDP) data used here are converted to international dollars using Purchasing Power Parity (PPP) rates, and rescaled to 2000 to give a common reference year. An international dollar has the same purchasing power in a given country as a United States Dollar in the United States. In other words, an international dollar buys an equivalent amount of goods or services in all countries.

Years Covered and Frequency of Update:
Data are available here for the years 1990, 2000, and 2003. However, the full datasets provided by the IEA span 1960-2004 for countries that are members of the Organization for Economic Co-operation and Development (OECD) and 1971-2004 for OECD non-members, although coverage varies. The IEA updates their energy data each year in June for OECD countries and in September for non-OECD countries, often revising data from earlier years.

Methodology:
World Resources Institute (WRI) calculates per GDP energy consumption with GDP data from the World Bank's World Development Indicators. A more complete description of GDP, PPP can be found at http://earthtrends.wri.org/searchable_db/variablenotes.cfm?varid=222&theme=5.

Basic energy statistics are collected by the IEA from a variety of sources. In OECD member countries, national administrations fill out five annual questionnaires. In non-OECD countries, statistics are collected from questionnaires, international organizations such as the United Nations, cooperation with national statistical bodies, and direct communication with energy consultants and companies. If data are not available from any of these sources, they are estimated by the IEA.

To facilitate comparisons among different sources of energy, the IEA measures the heat content of all energy commodities in tonnes (metric tons) of oil equivalent (toe). A tonne of oil equivalent measures the energy contained in a metric ton (1000 kg) of crude oil and is equal to 10 Exp. 7 kilocalories, 41.868 gigajoules, or 11,628 kilowatt-hours (kWh).

The energy produced by fossil fuels is calculated using conversion factors per unit mass of fuel (e.g. 10,000 kcal/kg of oil). Since energy sources such as coal and crude oil may vary in quality, the IEA typically uses specific conversion factors supplied by national administrations for the main categories of energy sources and uses (i.e., production, imports, exports). Energy sources categorized as petroleum products, however, have a single set of conversion factors for all countries.

The energy produced by non-fossil fuel sources is more complicated to measure; the IEA must first define a primary form of energy to measure, and then calculate the primary energy equivalent. The principle adopted by the IEA is that the primary energy form should be the first energy form downstream in the production process for which multiple energy uses are practical. Heat is therefore the primary form of energy for nuclear, geothermal, and solar thermal production. For hydro, wind, wave and photovoltaic solar production, total electricity is the primary form of energy. The IEA determines the physical energy content of the primary energy source using global or regional efficiency averages.

These statistics are expressed in terms of "net" calorific value, so the values reported here may be slightly lower than those in other statistical compendia which report energy in terms of "gross" calorific value.

Data Reliability:
The energy balances data are primarily based on well-established and institutionalized accounting methodologies, and are therefore considered reliable.

Energy production estimates from nuclear power and renewable sources (hydroelectric, solar, geothermal, and wind power) are calculated using a number of assumptions about primary energy forms and plant efficiencies. As a result, these values may be less reliable than estimates of energy produced from fossil fuels, and the share of renewables in total energy supply may appear different here than it would from other providers.

The data as received from the provider do not distinguish between no data and zero values. WRI has distinguished between the two where possible, but some values represented as zero should probably be indicated by ".." and vice-versa.

© OECD/IEA 2008

International Energy Agency (IEA) Statistics Division. 2006. Energy Balances of OECD Countries (2006 edition) and Energy Balances of Non-OECD Countries (2006 edition). Paris: IEA. Available at http://data.iea.org/ieastore/default.asp.

Development Data Group, The World Bank. 2006. 2006 World Development Indicators Online. Washington, DC: The World Bank. Available at: http://publications.worldbank.org/ecommerce/catalog/product?item_id=631625.