There have been several changes that affect comparability of incidence rates from year to year, as shown in the chart above. The North American Industry Classification System (NAICS) replaced the Standard Industrial Classification (SIC) system beginning with the 2003 survey of occupational injuries and illnesses.
Revisions to OSHA’s occupational injury and illness recordkeeping requirements went into effect in 2002 and therefore, these changes in record-keeping requirements affect comparison with earlier years (and also explains the break in the chart above).
Lastly, beginning with 1992, the Bureau of Labor Statistics (BLS) revised its annual survey to include only nonfatal cases and stopped publishing the incidence rate of lost workdays.