The Standard Industrial Classification (SIC) is a system used to categorize industries by assigning a unique code to each type of economic activity. Developed in the United States, it helps government agencies, researchers, and businesses analyze economic data and trends. Each SIC code consists of four digits, with the first two digits representing the major industry group and the last two digits providing more specific details about the industry. SIC codes are often used in conjunction with the North American Industry Classification System (NAICS), which replaced SIC in many applications. However, SIC codes are still relevant for historical data and certain regulatory purposes. They assist in identifying industries for statistical analysis, economic research, and policy-making.