The Standard Industrial Classification (SIC) and North American Industry Classification System (NAICS) are numerical classification systems that are used to group/classify like companies into industries for the purposes of collecting, analyzing, and publishing statistical data related to the U.S. business economy.

While NAICS has "officially" replaced SIC, many business directories and databases still use one or both of the systems. Therefore, it is important to know about both SIC and NAICS.

How does this help me?

Some library databases, books, and web sites allow you to search using SIC and/or NAICS codes, therefore, it is very important to know what the industry classification code is before beginning your research.

6-digit codes. NAICS was developed by the U.S., Canada and Mexico in 1997 to provide comparability in business statistics and to replace SIC.

NAICS is based on similar processes for production activities, with special attention given to emerging industries, service industries and advanced technologies.

NAICS is compatible with the United Nations International Standard Industrial Classification (ISIC).

NAICS editions: 1997, 2002, 2007, 2012.

4-digit codes. SIC classifies establishments by their primary activity focusing on similar products and services. Established in 1937, it was replaced by NAICS in 1997. Last updated in 1987, SIC is still used by some government agencies and in many databases.

• The United Nations International Standard Industrial Classification (ISIC)
  Classifies data according to kinds of economic activity in the fields of production, employment, gross domestic product and other statistical areas. ISIC is a basic tool for international comparability of data.
• NACE
  Statistical Classification of Economic Activities in the European Community.
• Industry Classification Benchmark (ICB)
  ICB is a company classification system developed by Dow Jones and FTSE. It is used to segregate markets into sectors within the macroeconomy. The ICB uses a system of 10 industries > divided into 19 supersectors > 41 sectors > 114 subsectors. Used by NASDAQ, NYSE and several other markets. Check out links to primary sources in this Wikipedia overview.
• Global Industry Classification Standard (GICS)
  GICS was developed by Standard & Poor's (S&P) and Morgan Stanley Capital International (MSCI) as a basis for S&P and MSCI financial market indexes. GICS consists of 10 sectors > 24 industry groups > 68 industries > 154 sub-industries. Similar to ICB.

According to NAICS Association, the NAICS taxonomy is based on a production-oriented, or supply-based, conceptual framework instead of an output-based framework of SIC. This means that producing units that use identical or similar production processes are grouped together in NAICS.

While many NAICS industries directly compare with SIC industries, a number of SIC industries were split or combined to form a new NAICS industry. SIC groups economic activity into 11 major divisions, while NAICS has 23 sectors.