This report includes data for 1965 through 2005. Data for the years prior to 1965 can be found in earlier reports in the series. Since the last publication of this series in 2003 (data compiled through 2002), many agencies have discontinued the collection of various data. This change is indicated on the tables, where applicable. Some data were derived from mathematical calculations and some show conversions from different units of measurement. Throughout the tables and text, billion denotes 109. The references cited in the text and in the tables are listed separately. Text references are listed in literature cited. The sources for data in the tables are listed in an annotated bibliography, which is cross-referenced to the tables.