The December 2002 Survey of Current Business (SCB) article on the 1997 I-O accounts, “Benchmark Input-Output Accounts of the United States, 1997,” explains all the definitions and conventions used in the creation of the accounts.  The article is available online at  Subsequent changes in classification and definition can be found in the October 2007 SCB article “U.S. Benchmark Input-Output Accounts, 2002,” available online at