Calculating Incidence Rates
Incidence rates show the relative level of injuries and illnesses among different industries, firms, or operations within a single firm. These rates help determine both problem areas and progress in preventing work-related injuries and illnesses.
A single injury or illness has a much greater effect on incidence rates in small establishments than on larger establishments. Any analysis must take this into account. Incidence rates take on more meaning for an employer when the injury and illness experience of his or her firm is compared with that of other employers doing similar work with workforces of similar size.
Evaluation of injury and illness data is a vital component of hazard identification and abatement. However, it is only one component of an effective evaluation. OSHA strongly advocates the use of multiple variables to evaluate the effectiveness of an employer’s safety and health program. While an injury and illness incident rate is a useful indicator of an establishment’s safety and health environment, reliance on only one indicator can lead to wrong conclusions.
Calculate an Incidence Rate
You can compute an occupational injury and illness incidence rate for all recordable cases or for cases that involved days away from work for your firm quickly and easily. The formula requires that you follow instructions in paragraph (a) below for the total recordable cases or those in paragraph (b) for cases that involved days away from work, and for both rates the instructions in paragraph (c).
(a) To find out the total number of recordable injuries and illnesses that occurred during the year, count the number of line entries on your OSHA Form 300, or refer to the OSHA Form 300A and sum the entries for columns (H), (I), and (J).
(b) To find out the number of injuries and illnesses that involved days away from work, count the number of line entries on your OSHA Form 300 that received a check mark in column (H), or refer to the entry for column (H) on the OSHA Form 300A.
(c) The number of hours all employees actually worked during the year. Refer to OSHA Form 300A and optional worksheet to calculate this number.
You can compute the incidence rate for all recordable cases of injuries and illnesses using the following formula:
Total number of injuries and illnesses X 200,000* ÷ Number of hours worked by all employees = Total recordable case rate
(*The 200,000 figure in the formula represents the number of hours 100 employees working 40 hours per week, 50 weeks per year would work, and provides the standard base for calculating incidence rate for calculating incidence rates.)
Alternatively you can compute the incidence rate for recordable cases involving days away from work, days of restricted work activity or job transfer (DART) using the following formula:
(Number of entries in column H + Number of entries in column I) X 200,000 ÷ Number of hours worked by all employees = DART incidence rate
You can use the same formula to calculate incidence rates for other variables such as cases involving restricted work activity (column (I) on Form 300A), cases involving skin disorders (column (M-2) on Form 300A), etc. Just substitute the appropriate total for these cases, from Form 300A, into the formula in place of the total number of injuries and illnesses.
For more information on how to compute your firm’s incidence rate, BLS.gov