Although we live in a society where safety is still largely measured through lagging indicators such as lost time injury frequency rates, I am often asked how these are calculated and what they are based on. Here follows a short explanation of incidence rates and the calculation thereof. An incidence rate of injuries and illnesses is computed by using the following formula: (Number of injuries and illnesses X 200,000) / Employee hours worked = Incidence rate) (The 200,000 hours in the formula represents the equivalent of 100 employees working 40 hours per week, 50 weeks per year, and provides the standard base for the incidence rates.) You can use the same formula to compute incidence rates for: • LTIFR – Lost Time Injuries. (Injuries resulting in any lost time at work) • DIFR – Disabling Injuries.(Injuries that result in disablement) • RIFR – Reportable Injuries. (As per legislative reporting requirements) • MIFR – Minor Injuries. (Injuries where no lost time was experienced) • TIFR – Total Injuries. (All injuries experienced) These measurements are ideal for monitoring and identifying trends as well as comparing performance against industry norms. As with all statistical calculations for it to add value we need to clearly define what we are measuring and ensure we continuously classify according to these parameters. Too often we find organizations including contractor or indirect labour hours but not the associated injuries/illnesses. For the calculation to be true we need to include both variables. Other rates you can compute The Severity Rate looks at incidents in terms of the actual number of days that were lost on average. To calculate the Severity Rate, you simply divide the number of lost workdays by the number of recordable incidents. If for example you lost a total of 24 workdays, as a result of four incidents, you’d be able to tell that the average incident cost you 6 workdays. Severity is based on time spent away from work, expressed as an average across the number of lost time injuries. Incidence rates are what are known as ―lagging indicators, because they describe past history. They tend to be most useful when you compare them over several periods, so you can identify trends. Most medium-sized or larger companies would benefit from computing these rates each month, and tracking the trends from month to month. If you start to notice that your rates are climbing, you need to investigate to determine what’s happening. If they’re declining, it’s either a sign that your workers are following safe practices and that your safety plan is working, or people have stopped reporting. The TIFR will give you a good indication where your problems are and is consequently, in my opinion, the most important lagging indicator to monitor. By monitoring, investigating and reporting on the TIFR you will be able to adjust the focus of your leading indicators, thereby reducing your LTIFR incidence. The following aspects are critical to ensuring statistics add value to our health and safety program: • Understanding the calculation and its various components. • Clearly identifying and understanding the various injury/illness classifications. • Correctly classifying according to these definitions. • Always remember incidence rates measure failure and should never be used as the only health and safety measurement tool. Trends identified by these rates will however afford valuable historical data allowing us to focus on underperforming areas of our safety program. • Program measurement should be by means of leading indicators and not limited to recorded incidents. Source: InGa Health & Safety Newsletter Volume 02 – Issue 03
