Impact of technological change on labor productivity in U.S. coal mines—Evidence from time series and cross sectional data

In this paper, we examine the impact of technological change (TC) on labor productivity in underground and surface mines. TC in the underground mines is the replacement of continuous machines for conventional miners between 1951 and 1970 and the recent penetration of longwall machines. In surface mines, TC consists of substitution of medium and large sized power shovels and draglines (PS&DLs) for smaller counterparts. Impact of these capital stocks vis-à-vis such other explanatory variables as seam thickness or strip ratio, utilization of capacity, captive vs non-captive mines, skilled labor, large sized mines and a dummy variable for coal mine regulations, on labor productivity is analysed by regressing the effects of these explanatory variables on labor productivity. The data used for the analysis include time series, as well as cross section data for mines in the Energy Information Administration's tapes for 1977. The analysis shows that adoption of newer technologies increases labor productivity in both mine types. Other variables that explain increases in productivity are increased seam thickness (in underground mines), exploitation of non-captive mines, use of skilled labor, and use of large mines. The variables explaining decreases in productivity are increased use of semi-skilled labor, strip ratio (in surface mines), mine accidents, and coal mine regulations.