This report summarizes key trends in carbon dioxide (CO2) emissions, fuel economy and technology usage related to model year (MY) 1975 through 2009 light-duty vehicles sold in the United States. Light-duty vehicles are those vehicles that EPA classifies as cars or light-duty trucks (sport utility vehicles or SUVs, vans, and pickup trucks with gross vehicle weight ratings up to 8500 pounds). The data in this report supersede the data in previous reports in this series. On September 15, 2009, EPA proposed the first-ever light-duty vehicle greenhouse gas emissions standards, under the Clean Air Act, for MY2012-2016 (74 Federal Register 49454, September 28, 2009). These proposed standards are part of a new, harmonized National Policy that also includes proposed corporate average fuel economy (CAFE) standards for the same years by the Department of Transportation's National Highway Traffic Safety Administration (NHTSA). Accordingly, while past reports in this series focused exclusively on fuel economy data, this year's report provides some key industry-wide tailpipe CO2 emissions data for the 1975 2009 time series as well. Tailpipe CO2 emissions data represent 90 to 95 percent of total light-duty vehicle greenhouse gas emissions. Section IV of this report discusses the CO2 emissions data in more detail and also provides guidance for how readers can calculate CO2 emissions values, not shown in Section IV, that are equivalent to other fuel economy values in this report.