For directions on reading the variable description see Data Dictionary Introduction .
Some persons work in more than one industry.
If persons listed more than one industry, the samples use the first one listed. Persons not currently employed were to give their most recent industry. For all years except 1920, the industries are classified according to the contemporary Census Bureau classification systems. The 1920 sample classifies industries according to the 1950 system. The meaning of the industry codes varies among years.