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. The codes can be very helpful in doing industry research.
The SIC code has been revised over the years and some code numbers have changed. It is important to be careful when comparing data from different publishers and over a long period of time. Beginning with the 1997 Economic Census, the Census Bureau began using a new North American Industrial Classification System (NAICS) which is more closely aligned with international codes.