The standard industry classification system used by U.S. Federal statistical agencies in classifying business establishments. NAICS is a two-through six-digit hierarchical classification system, offering five levels of detail. Each digit in the code is part of a series of progressively narrower categories, and an increasing number of significant digits in the code signify greater classification detail. Use of the standard provides uniformity and comparability in the presentation of statistical data. The equivalent system in Europe is NACE (Nomenclature Générale des Activités Économiques dans les Communautés Européennes). NACE is administered by the European Commission and subject to legislation at a European level which imposes the use of the classification uniformly within Member States. There is also an International Standard Industrial Classification in existence which is administered by the United Nations. The latest version of NACE (Rev2), is based on ISIC Rev 4 and adapted for European circumstances.
Source: Staffing Industry Analysts