Many business publications and databases use industry codes to organize data. American companies are grouped into industries according to their Standard Industrial Classification code (SIC), established by the Office of the Budget & Management (OMB). In 1997, OMB announced its decision to adopt the North American Industry Classification System (NAICS pronounced Nakes) as the industry classification system used by the statistical agencies of the United States.

North American Industry Classification System

The NAICS numbering system is a six-digit code. The first two digits designate the largest business sector. The third digit designates the sub sector, the fourth digit designates the industry group, and the fifth digit designates particular industries.  The last digit designates national industries. The first five digits are generally the same in all three countries.  

Standard Industrial Classification

The SIC numbering system uses is a four-digit code. The first two digits designate a general industrial sector.  The third digit designates the industry group, while the last digit specifies a more focused industry segment.

To begin your research, start by locating the codes for your industry.

North American Industry Classification System                    Lewis Ready Reference   HF 1042 N6

http://www.census.gov/epcd/www/naics.html

This site allows keyword searches for industries, in addition to providing NAICS/SIC conversion tables.

Standard Industrial Classification Manual                           Lewis Ready Reference   HF 1042 .S73 1987

http://www.osha.gov/oshstats/sicser.html

The codes can also be searched by keyword (e.g. automobiles)