The U.S. Energy Information Administration's report, U.S. Carbon Dioxide Emissions in 2009: A Retrospective Review, indicates that in 2009, energy-related carbon dioxide emissions in the United States saw their largest absolute and percentage decline (7 percent) since the start of EIA’s comprehensive record of annual energy data that begins in 1949. While emissions have declined in three out of the last four years, 2009 was exceptional. Emissions developments in 2009 reflected a combination of factors, including some particular to the economic downturn, other special circumstances during the year, and other factors that may reflect persistent trends in the U.S. economy and energy use.