Information on work stoppages is obtained from reports from major media sources, the Federal Mediation and Conciliation Service (FMCS), state labor market information offices, and the U.S. Bureau of Labor Statistics (BLS) Strike Reports from the Office of Employment and Unemployment Statistics. One or both parties involved in the work stoppage (the employer, the union or non-union organizations involved) are contacted by Work Stoppages program staff to verify the dates of the stoppage and the number of workers participating in the stoppage.
Data are based on the number of workers involved in or directly affected by the work stoppage. (For example, teacher work stoppage may involve closing schools and could impact additional staff.) Data are sometimes captured from third parties if either the organization or the union involved cannot provide detailed information or estimates. For example, BLS has used employment from state education department reports to most accurately identify workers involved in large work stoppages including teachers. If there are discrepancies between the available data sources, the most detailed information records available are typically utilized. Published monthly data may be revised if data sources are later found to provide more accurate details of a major work stoppage.
The number of workers listed as involved in a major work stoppage may differ from media reports and union bargaining unit information. This may have an impact on the work stoppage meeting the criteria for inclusion in the total estimate. For example, a bargaining unit with 1,200 workers having 800 confirmed workers involved in a work stoppage, would not meet inclusion criteria of 1,000 workers or more.
Major work stoppages are classified by industry in monthly and annual reporting to identify sectors of the economy where work stoppages occurred. Industry classification is based on the 2017 North American Industry Classification System (NAICS) and the Work Stoppages program staff determines the most representative NAICS code for the organization or establishments directly involved in the work stoppage.