The Standard Industrial Classification (SIC) is a system used to categorize industries based on their primary business activities. Developed in the United States, it assigns a unique four-digit code to each industry, allowing for easier data collection and analysis. This classification helps government agencies, researchers, and businesses understand economic trends and industry performance. SIC codes are often used in various applications, including economic research, regulatory compliance, and market analysis. While the SIC system has been largely replaced by the North American Industry Classification System (NAICS), it is still referenced in many contexts, especially for historical data and comparisons.