Census of Fatal Occupational Injuries - Hours-Based Rates

Fatality rates depict the risk of incurring a fatal occupational injury faced by all workers or a group of workers, such as workers in a certain occupation or industry, and can be used to compare risk among worker groups with varying employment levels. Since employment data are not collected by the Census of Fatal Occupational Injuries (CFOI), fatality rates have been calculated using employment estimates from the Current Population Survey (CPS), supplemented where needed with data from the U.S. Department of Defense. All the CFOI fatality rates published by BLS for the years 1992 through 2007 were employment-based, and measured the risk of fatal injury for those employed during a given period of time, regardless of hours worked.

Hours-based rates measure fatality risk per standardized length of exposure, and are generally considered more accurate than employment-based rates. Hours-based rates use the average number of employees at work and the average hours each employee works. Employment and hours-based rates will be similar for groups of workers who tend to work full-time. However, differences will be observed for worker groups who tend to have a high percentage of part-time workers, such as younger workers.

Hours worked data are also obtained from the CPS. The scope of CPS differs from that of CFOI in both the employment-based model and the hours-based model. Where these differences occur, CFOI adjusts fatality counts used in calculating the rates to maintain consistency between the rate numerator (number of fatalities) and the denominator (annual average employment and/or average hours at work). The employment-based fatality rate calculation excluded only workers under the age of 16. These workers will be excluded with the new hours-based rates as well, but volunteers and military personnel will also be excluded. CFOI has not been able to obtain reliable hours worked data for the resident military and volunteers are not included in the CPS data.

The table 2007 Fatality Rates (in PDF format) includes both hours-based and employment-based rates. However, hours-based fatality rates should not be directly compared to employment-based rates because of the differences in the numerators and denominators used.

The new rate methodology will be employed beginning with CFOI data for 2008 scheduled to be released in August 2009.

If you have any questions about the CFOI transition to hours-based rates, please call 202-691-6170 or email us.

Last Modified Date: June 2, 2009