The Structure of the Four-Digit SIC System
Although the U.S. federal government officially replaced SIC with NAICS in 1997, the 1987 SIC manual remains a vital reference in historical datasets and regulatory classifications [1]. The system is built around four levels of detail:
- Divisions: Represented by letters A through K (e.g., Division I represents Services).
- Major Groups: Two-digit codes aggregating industry groups (e.g., Major Group 73 represents Business Services).
- Industry Groups: Three-digit subdivisions (e.g., Industry Group 737 represents Computer Programming, Data Processing, and Other Computer Related Services).
- Specific Industries: The final four-digit code, such as SIC 7371 for Computer Programming Services.
Our database contains exactly 1,004 distinct four-digit SIC codes derived from the authoritative OSHA SIC manual [1].