Fatalities in Small Underground Coal Mines (1983) / Chapter Skim
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STATISTICAL ANALYSES OF SMALL UNDERGROUND COAL MINES
STATISTICAL ANALYSES OF SMALL UNDERGROUND COAL MINES
Pages 6-16
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Since over 90 percent of all mining in the United States is conventional or continuous mining, this means that the fatality rates corresponding to these methods must be substantially different. Second, the distribution of mining method must vary considerably across mine size.
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, there do not appear to be marked differences in the fatality rates of these two mining methods. Thus it does not appear as if mining method per se could explain any material amount of the elevated fatality rate in smaller mines.
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In our previous study we were able to obtain the then-current age distribution of miners in the major companies that operate underground coal mines by requesting those data directly from the coal companies. The 15 coal companies that responded represent approximately one half of the underground coal mining population of the United States.
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In contrast, only 4 percent of the larger mines were operational for so little time. This striking difference between small and large mines gives rise to several possible explanations for the association between mine size and fatality rates.
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No. of Quarters Operational Mine Size Total No.
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Hence only intermittency of operation could be investigated, and, as we have seen, mines that open and close repeatedly tend to have a higher fatality rate. Number of Runs A related hypothesis is that small mines that open and close regularly are at higher risk for a fatal accident than are those that are open continuously.
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From page 15... ...
That is, it could be that a small mine and large mine that have been active over the same period have equal fatality rates, but that, overall, smaller mines have higher fatality rates simply because they remain open for less time than do larger mines. To explore this possibility, we computed changes in mine fatality rates over time, focusing only on small mines open continuously for seven or more quarters.
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From page 16... ...
In every other state, mines with 1-50 employees account for no more than 5 percent of the total employee-hours. The data on seam thickness, age of miner, and mining method indicate that none of these factors has any substantial impact on the relationship between mine size and fatality rates.
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