Reports for 1970-1979 are based on the Standard Industrial Classification (Revised 1968); 1980-1982 are based on the SIC (Rev. 1980). A special summary vol. (Business monitor PA 1002.1) for the 1979 Census of production, based on the SIC (Rev. 1980) and also containing the 1979 Purchases inquiry, was published in 1983 under title: 1979 Census of production and purchases inquiry.