The Federal government classifies manufacturing and service industries and assigns each a Standard Industrial Classification (SIC) code number in order to promote the comparability of statistics. These SIC codes are hierarchical and may range from 2 to 8 digits long. For example:
|Major Group||37||Transportation equipment|
|371||Motor vehicles and equipment|
|3711||Motor vehicles and passenger car bodies|
The SIC code has been revised over the years and some code numbers have changed. Be careful when comparing data from different publishers and over a long period of time. Currently, most sources are using the 1992 revision.
Beginning with the 1997 Economic Census, the Census Bureau used an entirely new North American Industrial Classification System (NAICS) more closely aligned with international codes. NAICS was developed jointly by the U.S., Canada, and Mexico based on similar processes instead of by materials and breaks out many of the more recent industries.
Several new sectors were added: Information; Health Care and Social Assistance; and the Professional, Scientific, and Technical Services Sector. Commercial publications have started to convert to NAICS, but many still use SIC codes.