Age, Injuries, and Costs: A Case Study for U.S. Gold and Coal Mines

This paper focuses on the relationship between age and injuries in the mining industry—specifically, gold and coal—for the last two decades using publicly available data collected from a variety of sources.  In the U.S., the Department of Labor, through the Mine Safety and Health Administration (MSHA), regulates the mining industry. As per the Mine Act of 1977, MSHA is required to inspect surface (underground) mines at least two (four) times per year.  Such inspections form the basis of the publicly available data: Address & Employment (A&E) and Accident, Injury, and Illness (AI&I) files.

The A&E and AI&I provide company-level details in addition to any and all injuries that occurred in the metal/non-metal industry, along with coal.  Using these data we are able to characterize the injury rate and determine how it varies with a miner’s age (and experience).  Overall, we find a declining injury counts and rates, which is consistent with the literature.  For the 20-year period we study, the average injury rates are 5.64 and 9.41 percent for gold and coal, respectively.  Using the entire collection of mines contained in the MSHA files, we identify the 10 most commonly injured body parts and determine that injuries to finger(s) and back are the most frequent.  Using publicly available data released by emergency departments in American hospitals (i.e. Web-based Injury Statistics Query and Reporting System, WISQARS), we monetize the cost of these injuries—both in terms of the direct (i.e. medical) costs and the indirect (i.e. work loss) costs.  The enormity of the latter highlights the importance of measuring (or attempting to) such costs when calculating the total economic costs of accidents, injuries, illnesses, etc.   On average, the total economic cost of an injury in the mining industry is approximately $7,000 (as expressed in constant 2010 US$).  About 85 percent of this cost stems from lost time at work.  The severity of injury is assessed by the days of restricted, lost, or away from work.  We find that the days of restricted work far outnumbers the other two measures and increases with a miner’s age.  Coal miners experience more days away from work than do gold miners.

Due to the limitations presented by the AI&I data, we note that the average age of injured miners in our sample is younger than a nationally representative sample (as determined by the IPUMS-USA); the age distribution is skewed in the direction of a younger workforce.  Taking this into consideration, we perform an econometric analysis where we assess how the likelihood of a particular body area being injured is affected by the age of the miners, the mine size, and the type of operation.  Conditional on an injury occurring, we find, regardless of commodity, that younger miners are more likely to injure their upper (i.e. finger, hand, or wrist) or lower (i.e. knee, ankle, or foot) extremities.  Middle-aged workers are more likely to injure their back or shoulder.  We perform a series of robustness checks that reinforce these findings.