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SIC, or Standard Industrial Classification, is a system created in the 1930s, last revised in 1987. It's a scheme by which each product or service, whether manufacturing, wholesaling, or retailing, is identified by a 4-digit number with added-on extensions to further delineate specific businesses under a major heading or industry group.

NAICS (rhymes with "bakes"), or the North American Industry Classification System, was created in 1997, and has been revised in 2002 and 2007. This system was developed following the 1992 passage of the NAFTA (the North American Free Trade Agreement), and allows for better identification of business industries on the continent (the US, Canada, and Mexico). The system incorporates the same general industry group/business line theme used in SIC; however, numbers were lengthened to reflect added variety of business enterprises and activities. Consider that in 1987, business like the Internet and telecommunications (cell phones) didn't exist, and many new types of business services have been introduced since then. This system includes enhanced coverage of newly-introduced businesses and services. Numbers are 6-digits long, and there is occassionally no correlation between the two systems; in other words, in some cases, there may be a NAICS number, but no SIC, or merely a very general industry area in SIC.

The NAICS system replaced SIC, at least in the official reporting of business activities from federal statistical agencies; however, many other kinds of agencies and many information products, which feature these numbers in organization and searching of their product, continue to cite and use SIC numbers. Therefore, it's advisable to have a researcher of business information look up SIC and NAICS numbers related to a particular business when beginning research. This way, they'll be ready for whichever sources they use and whatever they might encounter in their research.

Finding and Understanding NAICS/SIC