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Mass Layoff Statistics

Change in Industry Classification System

December 2001 mass layoff monthly data and fourth quarter 2001 extended mass layoff data were the last from the Mass Layoff Statistics (MLS) program using the 1987 Standard Industrial Classification (SIC) system. Beginning with the release of data for January 2002 in late February 2002, the program switched to the 2002 version of the North American Industry Classification System (NAICS) as the basis for the assignment and tabulation of economic data by industry. NAICS is the product of a cooperative effort on the part of the statistical agencies of the United States, Canada, and Mexico. Due to differences in NAICS and SIC structures, data for 2002 are not comparable to the SIC-based data for earlier years. However, the historical industry series from April 1995 (second quarter 1995 for extended mass layoffs) through 2001 are available on both SIC and NAICS bases. 

NAICS uses a production-oriented approach to categorize economic units. Units with similar production processes are classified in the same industry. NAICS focuses on how products and services are created, as opposed to the SIC focus on what is produced. This approach yields significantly different industry groupings than those produced by the SIC approach.

Users interested in more information about NAICS can access the BLS Web page at or the Bureau of the Census Web page at


Last Modified Date: March 5, 2003