1. Data from International Energy Administration, http://www.iea.org/.
2. Source: US dollar GNP data from World Bank STARS database. Energy data from IEA: World Energy Statistics and Balance database, as cited in Energy Information Administration, Energy Use and Carbon Emissions: Some International Comparisons, DOE/EIA-0579 (Washington, DC, March 1994), p. 19.
3. Adapted from data from American Council for Capital Formation, 2000.
4. US EPA, National Air Pollutant Emissions Trends Report 1900–1998, March, 2000, EPA 454/R-00-02.