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Mass Layoff Statistics

Mass Layoff Statistics—Data Revision Procedure

Every five years the North American Industry Classification System (NAICS) is updated to reflect changes in the U.S. economy, recognize new and emerging industries, and strive for international compatibility. In the MLS program, industry information for employers is obtained from the BLS Quarterly Census of Employment and Wages (QCEW) program.

NAICS 2012 Changes

The conversion to NAICS 2012 resulted in revisions reflecting increased detail in the electric power generation industry, increased detail in certain industries within the specialty trade contractors subsector; redefinition of merchant wholesalers of durable goods; consolidation of numerous smaller manufacturing and retail industries into larger ones; and changes to numeric codes of some manufacturing, retail, and food service industries. Several industry titles and descriptions also were updated. This revision was introduced by the Bureau of Labor Statistics (BLS) with the release of first quarter 2011 Quarterly Census of Employment and Wages (QCEW) data. A complete list of NAICS 2012 industries with further information on the changes associated with moving from the 2007 NAICS is available on the Census Bureau’s NAICS page, which can be accessed at

Implementation in the MLS Program

The MLS program implemented the 2012 version of NAICS beginning with January 2012 mass layoff data, released on February 23, 2012. The first publication of quarterly extended mass layoff data using NAICS 2012 was issued with the release of first quarter 2012 data on May 16, 2012. MLS data are published at the major sector level and the subsector level (3-digit NAICS).

Layoff events prior to 2012 assigned a NAICS 2007 industry that directly transferred to a NAICS 2012 industry were changed to the NAICS 2012 industry in order to minimize the number of data series breaks. This resulted in slight, one-time revisions to published data for NAICS 321 (wood product manufacturing), NAICS 337 (furniture and related product manufacturing, NAICS 443 (electronics and appliance stores), and NAICS 451 (sports, hobby, music instrument, book stores). There were no revisions at the major industry sector level.

In addition, there were eight NAICS 2007 industries that split into two or more industries in NAICS 2012. In pre-2012 events where the industries exist in both NAICS 2007 and NAICS 2012, the original industries were retained. This occurred in 6 of the 8 split industries. For the remaining two splits, NAICS 221119 (other electric power generation) was changed to NAICS 221118 (other electric power generation) and NAICS 334119 (other computer peripheral equipment manufacturing) was changed to NAICS 334118 (computer terminal and other peripheral equipment manufacturing). MLS data for events in these split industries beginning in 2012 are not strictly comparable to pre-2012 information, though the differences are not likely to be significant. In addition, there were no data revisions to published MLS data resulting from split industries. The MLS table displaying extended mass layoff events and separations in information technology-producing industries has been updated using NAICS 2012. Previously, this table followed definitions based on NAICS 2002.

Previous Industry Changes in the MLS Program

The MLS program switched from the Standard Industrial Classification (SIC) system to the North American Industry Classification System (NAICS) in 2002. More information on this change is available at

In 2008, the MLS program converted from NAICS 2002 to NAICS 2007. More information on this change is available at


Last Modified Date: May 16, 2012