A four-digit classification system developed in the 1930's. No longer being revised, but still commonly used in many business databases. Some business data providers have added specificity to the SIC by adding extra digits, but these aren't standardized. An example of 6-digit codes is from Centurion Lists.
Maintained by the U.N. Statistics Division. Used in a number of international databases, such as ILO's LABORSTA. Rev.4 is the current version. See link on sidebar at the ISIC site to other available classifications.
