The North American Industry Classification System (NAICS) is the hierarchical, numerical system used by the Federal government to classify businesses by industry, in order to collect, analyze, and publish statistical data related to the U.S. business economy. This system was created to accommodate new industries and standardize data with Canada and Mexico.  While it replaces the Standard Industrial Classification (SIC) System, some resources still use the old SIC codes.

Use the official NAICS site to identify the NAICS and/or SIC codes for your topic. 

Note:

• Separate codes exist for manufacturers, retailers, and wholesalers.

• Some resources may include only a company's assigned "primary" industry code.  Primary codes apply to the company's main line of business. "Secondary" codes may appear if a company has multiple lines of business.

• Official NAICS website
• NAICS Association
• SIC Manual

These resources either contain SIC or NAICS indexes, or else organize content or permit searching by industry codes or categories. Some include business or product rankings by industrial code or sector.

Resources vary in the specificity of industry categories and sub-categories. Some include only the broader classification.

To determine the industry code assigned to a company, start with a company directory. For industry ratios, consult the ratio guide.

Once you have your codes, use them to find articles, data, companies or rankings by industry.