Industrial Classification Codes 

Official, numerical classification systems (Standard Industrial Classification (SIC) and North American Industry Classification System (NAICS)), enable the federal government to collect and classify data on business activity in the U.S.  A modified form, called SITC, pertains to international business enterprises.

SIC Hierarchy
 
The old hierarchy, SIC, allows related industries to be classed close together.

Example:  The SIC code for printing, publishing and allied industries is 27. Getting more specific, the industry group number for newspapers is 271; periodicals is 272, and books is 273. Adding another digit(s) would allow one to focus even more specifically to special types of book publishing.
 
Most of the SIC codes you will see will be at the 4-digit level of specificity.

NAICS Hierarchy

The hierarchical NAICS system replaced the 1987 SIC in 1997 to accommodate new industries and harmonize the separate schemes used by the U.S., Canada and Mexico. While you may see resources that use either scheme, the government officially converted to NAICS with the release of the 1999 Economic Census. Codes at the 6-digit level are typical.

North American Product Classification System

NAPCS is a new system under development to improve product data for service industries.
More information is available from these Census websites:

NAPCS Overview

NAPCS Home Page

Determining Your Industry's Codes:

Many resources for business use SIC or NAICS codes to sort information by industry or rank information within an industry. To determine the official code for your industry, consult these print or online manuals.

SIC or NAICS Indexes: 

Electronic: Standard Industrial Classification (SIC) Manual
Print: General Reference HF 1042.S731 1986 (also in Government Publications)

Electronic: North American Industry Classification System
Print: General Reference HF1042.N6 2002 (also in Research Consultation Office)

Related Link:

NAICS web site at Texas A&M

Finding Companies and Information by Industry or Industry Codes: 

Many print and electronic resources contain SIC or NAICS indexes. Others organize information or permit searching by industry categories or codes.

To determine the industry code assigned to a company, start with a company profile in a print or electronic company directory.

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

Ward's Business Directory
General Reference HG 4057.A1W35

D & B Million Dollar Directory
General Reference HC 102.D8

Standard & Poor Register of Corporations
General Reference HG 4057.A1S8

Market Share Reporter
General Reference HF 5410.M35

Thomas Register
General Reference T 12.T6

Hoover's Handbook of World Business
General Reference HG 4009.H66

Hoover's Master List of Major U.S. Companies
General Reference HG 5035.H66 

ReferenceUSA : an online phonebook  (All JHU (incl. International))

Dun & Bradstreet  (All JHU (incl. International))

Mergent online  (All US JHU)

Mergent Online enables one to retrieve a list of public companies by primary and/or secondary industry codes through the Advanced Search screen.  Primary codes represent the main line of business; secondary codes enable one to capture more companies that serve a particular industry.

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