NOTE: 2000 data for passenger-miles do not include numbers for transit or general aviation.
Energy use: U.S. Department of Energy, Energy Information Administration, Annual Energy Review, DOE/EIA 0384(2000) (Washington DC: August 2001).
Gross Domestic Product: U.S. Department of Commerce (USDOC), Bureau of Economic Analysis, available at http://www.bea.doc.gov/, as of January 2001.
Passenger-miles: U.S. Department of Transportation, Bureau of Transportation Statistics, National Transportation Statistics 2001, available at http://www.bts.gov.
Population: USDOC, U.S. Census Bureau, available at http://www.census.gov/, as of January 2001.