| Specification | Baseline (Hours Worked) | Employees | Tonnage | |||
Model |
Public Fields Only |
Confidential Fields |
Public Fields Only |
Confidential Fields |
Public Fields Only |
Confidential Fields |
| Mine/Controller Size Units: | 100 Quarterly FTEs |
100 Quarterly FTEs |
100 Employees |
100 Employees |
Millions of Tons |
Millions of Tons |
| Union | 0.228*** | 0.240** | 0.184** | 0.207** | 0.135* | 0.090 |
| (0.08) | (0.10) | (0.09) | (0.10) | (0.07) | (0.09) | |
| Union X Mine Size | -0.113* | -0.170*** | -0.119 | -0.196*** | -0.180 | -0.242* |
| (0.07) | (0.05) | (0.08) | (0.06) | (0.15) | (0.13) | |
| Mine Size | 0.301*** | 0.378*** | 0.326*** | 0.435*** | 0.495*** | 0.624*** |
| (0.05) | (0.06) | (0.07) | (0.07) | (0.12) | (0.16) | |
| Log of Controller Size | 0.111*** | 0.102*** | 0.134*** | 0.123*** | 0.123*** | 0.112*** |
| (0.01) | (0.02) | (0.02) | (0.02) | (0.01) | (0.02) | |
| Lost-Day Injuries in Prev. Year | 0.026*** | 0.029*** | 0.026*** | 0.029*** | 0.037*** | 0.041*** |
| (0.01) | (0.01) | (0.01) | (0.01) | (0.01) | (0.00) | |
| Penalty Pts. in Prev. Year | 0.065*** | 0.060*** | 0.066*** | 0.060*** | 0.075*** | 0.069*** |
| (0.01) | (0.01) | (0.01) | (0.01) | (0.01) | (0.01) | |
| Mine Age | 0.011*** | 0.012*** | 0.011*** | 0.012*** | 0.012*** | 0.012*** |
| (0.00) | (0.00) | (0.00) | (0.00) | (0.00) | (0.00) | |
| Productivity | -0.014*** | -0.014*** | -0.017*** | -0.017*** | -0.032*** | -0.034*** |
| (0.00) | (0.00) | (0.00) | (0.00) | (0.00) | (0.01) | |
| NIOSH Longwall Dummy | 0.143 | 0.134 | 0.277* | |||
| (0.15) | (0.15) | (0.14) | ||||
| Number of Coal Beds | -0.071 | -0.078 | -0.017 | |||
| (0.13) | (0.13) | (0.13) | ||||
| Avg. Coal Bed Thickness (yds.) | 0.014 | 0.008 | 0.025 | |||
| (0.05) | (0.05) | (0.05) | ||||
| Subsidiary Indicator | 0.130** | 0.105* | 0.151** | |||
| (0.06) | (0.06) | (0.06) | ||||
| Pct. Captive Production | -0.039 | -0.040 | -0.019 | |||
| (0.06) | (0.06) | (0.06) | ||||
| Recoverable Reserves | -0.000*** | -0.000** | -0.000* | |||
| (0.00) | (0.00) | (0.00) | ||||
| Augur Subunit Dummy | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) |
| Culm/Refuse Subunit Dummy | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) |
| Dredge Subunit Dummy | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) |
| Ind. Shop/Yard Subunit Dummy | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) |
| Mill/Prep. Plant Subunit Dummy | -0.061 | -0.062 | -0.049 | -0.052 | 0.057 | 0.076 |
| (0.11) | (0.11) | (0.11) | (0.11) | (0.10) | (0.11) | |
| Other Mining Subunit Dummy | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) |
| Strip/Quarry/Pit Subunit Dummy | -1.183*** | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) |
| (0.08) | ||||||
| Surface at Underground Subunit | -0.022 | -0.017 | -0.028 | -0.018 | -0.016 | -0.004 |
| Dummy | (0.05) | (0.06) | (0.05) | (0.06) | (0.05) | (0.06) |
| Underground Subunit Dummy | (dropped) | (dropped) | 1.202*** | (dropped) | 1.196*** | (dropped) |
| (0.08) | (0.08) | |||||
| Pct. Continuous Mining Method | 0.004*** | 0.005*** | 0.005*** | |||
| (0.00) | (0.00) | (0.00) | ||||
| Pct. Conventional Mining Method | 0.006*** | 0.006*** | 0.006*** | |||
| (0.00) | (0.00) | (0.00) | ||||
| Pct. Longwall Mining Method | 0.005** | 0.005** | 0.007*** | |||
| (0.00) | (0.00) | (0.00) | ||||
| Pct. Shortwall Mining Method | 0.012** | 0.012** | 0.013** | |||
| (0.01) | (0.01) | (0.01) | ||||
| MSHA Coal District 1 Dummy | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) |
| MSHA Coal District 2 Dummy | -0.664*** | -0.819*** | -0.639*** | -0.793*** | -0.849*** | -0.978*** |
| (0.14) | (0.13) | (0.14) | (0.13) | (0.14) | (0.14) | |
| MSHA Coal District 3 Dummy | -0.479*** | -0.440*** | -0.465*** | -0.436*** | -0.662*** | -0.625*** |
| (0.15) | (0.14) | (0.15) | (0.14) | (0.15) | (0.15) | |
| MSHA Coal District 4 Dummy | -0.153 | -0.161 | -0.153 | -0.149 | -0.348** | -0.318** |
| (0.15) | (0.15) | (0.15) | (0.15) | (0.15) | (0.16) | |
| MSHA Coal District 5 Dummy | -0.621*** | -0.614*** | -0.611*** | -0.604*** | -0.803*** | -0.784*** |
| (0.14) | (0.13) | (0.14) | (0.13) | (0.14) | (0.14) | |
| MSHA Coal District 6 Dummy | -0.240* | -0.332** | -0.225 | -0.309** | -0.428*** | -0.498*** |
| (0.14) | (0.13) | (0.14) | (0.13) | (0.14) | (0.14) | |
| MSHA Coal District 7 Dummy | -0.053 | -0.142 | -0.028 | -0.113 | -0.230 | -0.303** |
| (0.15) | (0.14) | (0.15) | (0.14) | (0.15) | (0.15) | |
| MSHA Coal District 8 Dummy | -0.328 | -0.219 | -0.325 | -0.220 | -0.433* | -0.327 |
| (0.24) | (0.20) | (0.24) | (0.20) | (0.26) | (0.20) | |
| MSHA Coal District 9 Dummy | 0.270 | 0.266 | 0.255 | 0.252 | 0.032 | 0.003 |
| (0.18) | (0.20) | (0.18) | (0.20) | (0.18) | (0.19) | |
| MSHA Coal District 10 Dummy | -0.054 | -0.097 | -0.013 | -0.047 | -0.122 | -0.116 |
| (0.20) | (0.20) | (0.19) | (0.20) | (0.20) | (0.21) | |
| MSHA Coal District 11 Dummy | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) |
| MSHA Coal District 12 Dummy | -0.477*** | -0.569*** | -0.455*** | -0.546*** | -0.658*** | -0.735*** |
| (0.14) | (0.13) | (0.14) | (0.13) | (0.14) | (0.14) | |
| Quarter Dummy - 1993q1 | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) |
| Quarter Dummy - 1993q2 | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) |
| Quarter Dummy - 1993q3 | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) |
| Quarter Dummy - 1993q4 | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) |
| Quarter Dummy - 1994q1 | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) |
| Quarter Dummy - 1994q2 | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) |
| Quarter Dummy - 1994q3 | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) |
| Quarter Dummy - 1994q4 | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) |
| Quarter Dummy - 1995q1 | -1.126*** | (dropped) | -1.072*** | (dropped) | -1.077*** | (dropped) |
| (0.12) | (0.13) | (0.13) | ||||
| Quarter Dummy - 1995q2 | -1.096*** | (dropped) | -1.063*** | (dropped) | -1.070*** | (dropped) |
| (0.12) | (0.13) | (0.13) | ||||
| Quarter Dummy - 1995q3 | -1.261*** | (dropped) | -1.223*** | (dropped) | -1.225*** | (dropped) |
| (0.12) | (0.12) | (0.13) | ||||
| Quarter Dummy - 1995q4 | -1.337*** | (dropped) | -1.277*** | (dropped) | -1.284*** | (dropped) |
| (0.12) | (0.12) | (0.12) | ||||
| Quarter Dummy - 1996q1 | -1.388*** | (dropped) | -1.344*** | (dropped) | -1.355*** | (dropped) |
| (0.13) | (0.13) | (0.13) | ||||
| Quarter Dummy - 1996q2 | -1.329*** | (dropped) | -1.286*** | (dropped) | -1.292*** | (dropped) |
| (0.12) | (0.12) | (0.13) | ||||
| Quarter Dummy - 1996q3 | -1.330*** | (dropped) | -1.294*** | (dropped) | -1.294*** | (dropped) |
| (0.12) | (0.13) | (0.13) | ||||
| Quarter Dummy - 1996q4 | -1.321*** | (dropped) | -1.285*** | (dropped) | -1.294*** | (dropped) |
| (0.12) | (0.13) | (0.13) | ||||
| Quarter Dummy - 1997q1 | -1.390*** | (dropped) | -1.357*** | (dropped) | -1.365*** | (dropped) |
| (0.12) | (0.13) | (0.13) | ||||
| Quarter Dummy - 1997q2 | -1.350*** | (dropped) | -1.315*** | (dropped) | -1.323*** | (dropped) |
| (0.13) | (0.13) | (0.13) | ||||
| Quarter Dummy - 1997q3 | -1.401*** | (dropped) | -1.370*** | (dropped) | -1.370*** | (dropped) |
| (0.12) | (0.13) | (0.13) | ||||
| Quarter Dummy - 1997q4 | -1.406*** | (dropped) | -1.369*** | (dropped) | -1.374*** | (dropped) |
| (0.12) | (0.12) | (0.13) | ||||
| Quarter Dummy - 1998q1 | -1.366*** | -1.390*** | -1.294*** | -1.321*** | -1.307*** | -1.295*** |
| (0.13) | (0.12) | (0.13) | (0.12) | (0.13) | (0.13) | |
| Quarter Dummy - 1998q2 | -1.356*** | -1.390*** | -1.305*** | -1.341*** | -1.311*** | -1.307*** |
| (0.13) | (0.12) | (0.13) | (0.12) | (0.13) | (0.12) | |
| Quarter Dummy - 1998q3 | -1.235*** | -1.266*** | -1.212*** | -1.247*** | -1.215*** | -1.209*** |
| (0.13) | (0.12) | (0.13) | (0.12) | (0.13) | (0.12) | |
| Quarter Dummy - 1998q4 | -1.286*** | -1.320*** | -1.255*** | -1.290*** | -1.273*** | -1.270*** |
| (0.13) | (0.12) | (0.13) | (0.12) | (0.13) | (0.13) | |
| Quarter Dummy - 1999q1 | -1.254*** | -1.279*** | -1.198*** | -1.216*** | -1.222*** | -1.225*** |
| (0.13) | (0.11) | (0.13) | (0.11) | (0.13) | (0.12) | |
| Quarter Dummy - 1999q2 | -1.290*** | -1.315*** | -1.261*** | -1.281*** | -1.286*** | -1.292*** |
| (0.13) | (0.11) | (0.13) | (0.12) | (0.13) | (0.12) | |
| Quarter Dummy - 1999q3 | -1.254*** | -1.280*** | -1.232*** | -1.252*** | -1.250*** | -1.255*** |
| (0.13) | (0.11) | (0.13) | (0.12) | (0.13) | (0.12) | |
| Quarter Dummy - 1999q4 | -1.335*** | -1.361*** | -1.307*** | -1.328*** | -1.333*** | -1.340*** |
| (0.13) | (0.11) | (0.13) | (0.11) | (0.13) | (0.11) | |
| Quarter Dummy - 2000q1 | -1.308*** | -1.324*** | -1.238*** | -1.250*** | -1.272*** | -1.269*** |
| (0.13) | (0.11) | (0.13) | (0.12) | (0.14) | (0.12) | |
| Quarter Dummy - 2000q2 | -1.277*** | -1.305*** | -1.231*** | -1.257*** | -1.256*** | -1.267*** |
| (0.13) | (0.11) | (0.13) | (0.12) | (0.13) | (0.12) | |
| Quarter Dummy - 2000q3 | -1.171*** | -1.199*** | -1.132*** | -1.156*** | -1.155*** | -1.165*** |
| (0.13) | (0.11) | (0.13) | (0.11) | (0.13) | (0.12) | |
| Quarter Dummy - 2000q4 | -1.134*** | -1.156*** | -1.120*** | -1.137*** | -1.146*** | -1.149*** |
| (0.12) | (0.11) | (0.13) | (0.11) | (0.13) | (0.11) | |
| Quarter Dummy - 2001q1 | -1.134*** | -1.153*** | -1.065*** | -1.074*** | -1.098*** | -1.094*** |
| (0.13) | (0.11) | (0.13) | (0.11) | (0.13) | (0.12) | |
| Quarter Dummy - 2001q2 | -1.022*** | -1.047*** | -0.972*** | -0.994*** | -0.997*** | -1.004*** |
| (0.13) | (0.11) | (0.13) | (0.11) | (0.13) | (0.12) | |
| Quarter Dummy - 2001q3 | -1.101*** | -1.121*** | -1.056*** | -1.074*** | -1.069*** | -1.073*** |
| (0.13) | (0.11) | (0.13) | (0.11) | (0.13) | (0.11) | |
| Quarter Dummy - 2001q4 | -1.194*** | -1.209*** | -1.161*** | -1.174*** | -1.177*** | -1.177*** |
| (0.12) | (0.11) | (0.13) | (0.11) | (0.13) | (0.11) | |
| Quarter Dummy - 2002q1 | -1.273*** | -1.289*** | -1.232*** | -1.245*** | -1.251*** | -1.251*** |
| (0.13) | (0.11) | (0.13) | (0.11) | (0.13) | (0.11) | |
| Quarter Dummy - 2002q2 | -1.310*** | -1.339*** | -1.280*** | -1.306*** | -1.301*** | -1.313*** |
| (0.13) | (0.11) | (0.13) | (0.12) | (0.13) | (0.12) | |
| Quarter Dummy - 2002q3 | -1.364*** | -1.391*** | -1.362*** | -1.386*** | -1.374*** | -1.384*** |
| (0.12) | (0.11) | (0.13) | (0.11) | (0.13) | (0.12) | |
| Quarter Dummy - 2002q4 | -1.370*** | -1.403*** | -1.323*** | -1.353*** | -1.347*** | -1.362*** |
| (0.13) | (0.11) | (0.13) | (0.11) | (0.13) | (0.12) | |
| Quarter Dummy - 2003q1 | -1.269*** | -1.301*** | -1.211*** | -1.235*** | -1.243*** | -1.255*** |
| (0.13) | (0.11) | (0.13) | (0.12) | (0.13) | (0.12) | |
| Quarter Dummy - 2003q2 | -1.205*** | -1.247*** | -1.149*** | -1.185*** | -1.175*** | -1.198*** |
| (0.12) | (0.11) | (0.13) | (0.11) | (0.13) | (0.12) | |
| Quarter Dummy - 2003q3 | -0.953*** | -0.997*** | -0.931*** | -0.969*** | -0.955*** | -0.981*** |
| (0.13) | (0.11) | (0.13) | (0.11) | (0.13) | (0.12) | |
| Quarter Dummy - 2003q4 | -1.155*** | -1.191*** | -1.113*** | -1.148*** | -1.139*** | -1.162*** |
| (0.13) | (0.11) | (0.13) | (0.12) | (0.13) | (0.12) | |
| Quarter Dummy - 2004q1 | -1.062*** | -1.092*** | -1.017*** | -1.040*** | -1.041*** | -1.053*** |
| (0.13) | (0.12) | (0.13) | (0.12) | (0.14) | (0.12) | |
| Quarter Dummy - 2004q2 | -0.960*** | -0.989*** | -0.888*** | -0.915*** | -0.907*** | -0.922*** |
| (0.13) | (0.12) | (0.13) | (0.12) | (0.14) | (0.12) | |
| Quarter Dummy - 2004q3 | -0.964*** | -0.990*** | -0.902*** | -0.920*** | -0.914*** | -0.922*** |
| (0.13) | (0.11) | (0.13) | (0.12) | (0.13) | (0.12) | |
| Quarter Dummy - 2004q4 | -1.006*** | -1.025*** | -0.958*** | -0.972*** | -0.975*** | -0.980*** |
| (0.13) | (0.11) | (0.13) | (0.12) | (0.13) | (0.12) | |
| Quarter Dummy - 2005q1 | -1.022*** | -1.053*** | -0.976*** | -0.999*** | -0.997*** | -1.010*** |
| (0.13) | (0.11) | (0.13) | (0.12) | (0.13) | (0.12) | |
| Quarter Dummy - 2005q2 | -1.061*** | -1.098*** | -1.028*** | -1.056*** | -1.045*** | -1.062*** |
| (0.13) | (0.11) | (0.13) | (0.12) | (0.13) | (0.12) | |
| Quarter Dummy - 2005q3 | -1.025*** | -1.064*** | -0.981*** | -1.013*** | -0.983*** | -1.005*** |
| (0.13) | (0.11) | (0.13) | (0.11) | (0.13) | (0.12) | |
| Quarter Dummy - 2005q4 | -0.967*** | -1.005*** | -0.941*** | -0.972*** | -0.937*** | -0.955*** |
| (0.13) | (0.12) | (0.13) | (0.12) | (0.14) | (0.12) | |
| Quarter Dummy - 2006q1 | -0.824*** | -0.855*** | -0.788*** | -0.812*** | -0.787*** | -0.801*** |
| (0.13) | (0.12) | (0.13) | (0.12) | (0.14) | (0.12) | |
| Quarter Dummy - 2006q2 | -0.669*** | -0.707*** | -0.625*** | -0.656*** | -0.627*** | -0.648*** |
| (0.13) | (0.11) | (0.13) | (0.11) | (0.14) | (0.12) | |
| Quarter Dummy - 2006q3 | -0.692*** | -0.728*** | -0.686*** | -0.715*** | -0.674*** | -0.691*** |
| (0.13) | (0.11) | (0.13) | (0.11) | (0.13) | (0.11) | |
| Quarter Dummy - 2006q4 | -0.891*** | -0.924*** | -0.850*** | -0.880*** | -0.833*** | -0.850*** |
| (0.13) | (0.12) | (0.13) | (0.12) | (0.13) | (0.12) | |
| Quarter Dummy - 2007q1 | -0.734*** | -0.748*** | -0.669*** | -0.673*** | -0.663*** | -0.655*** |
| (0.13) | (0.12) | (0.13) | (0.12) | (0.13) | (0.12) | |
| Quarter Dummy - 2007q2 | 0.304** | 0.264** | 0.338*** | 0.306*** | 0.354*** | 0.337*** |
| (0.13) | (0.11) | (0.13) | (0.11) | (0.13) | (0.11) | |
| Quarter Dummy - 2007q3 | 0.491*** | 0.471*** | 0.515*** | 0.497*** | 0.532*** | 0.530*** |
| (0.13) | (0.11) | (0.12) | (0.11) | (0.12) | (0.11) | |
| Quarter Dummy - 2007q4 | 0.441*** | 0.433*** | 0.444*** | 0.443*** | 0.438*** | 0.450*** |
| (0.12) | (0.11) | (0.11) | (0.11) | (0.12) | (0.11) | |
| Quarter Dummy - 2008q1 | 0.205** | 0.198** | 0.251** | 0.255*** | 0.222** | 0.240** |
| (0.10) | (0.10) | (0.10) | (0.09) | (0.10) | (0.10) | |
| Quarter Dummy - 2008q2 | 0.096 | 0.097 | 0.117 | 0.130 | 0.075 | 0.099 |
| (0.10) | (0.09) | (0.09) | (0.09) | (0.09) | (0.09) | |
| Quarter Dummy - 2008q3 | 0.107 | 0.116 | 0.118 | 0.131 | 0.091 | 0.120 |
| (0.09) | (0.08) | (0.09) | (0.08) | (0.09) | (0.09) | |
| Quarter Dummy - 2008q4 | -0.008 | 0.007 | -0.003 | 0.020 | -0.032 | 0.005 |
| (0.09) | (0.08) | (0.09) | (0.08) | (0.09) | (0.08) | |
| Quarter Dummy - 2009q1 | 0.019 | 0.018 | 0.015 | 0.025 | 0.023 | 0.034 |
| (0.09) | (0.09) | (0.08) | (0.08) | (0.09) | (0.08) | |
| Quarter Dummy - 2009q2 | 0.040 | 0.035 | 0.009 | 0.015 | 0.019 | 0.023 |
| (0.08) | (0.08) | (0.07) | (0.07) | (0.07) | (0.07) | |
| Quarter Dummy - 2009q3 | -0.029 | -0.034 | (dropped) | (dropped) | (dropped) | (dropped) |
| (0.07) | (0.07) | |||||
| Quarter Dummy - 2009q4 | (dropped) | (dropped) | 0.005 | 0.017 | -0.009 | 0.001 |
| (0.08) | (0.08) | (0.08) | (0.08) | |||
| Constant | 8.331*** | 7.978*** | 7.120*** | 7.939*** | 7.709*** | 8.437*** |
| (0.19) | (0.24) | (0.20) | (0.24) | (0.23) | (0.27) | |
| Observations | 23,349 | 16,767 | 22,679 | 16,305 | 22,679 | 16,305 |
| # of Union Mines / # of Total Mines | 227 / 1,517 | 151 / 1,113 | 227 / 1,512 | 151 / 1,108 | 227 / 1,512 | 151 / 1,108 |
| R2 | 0.53 | 0.56 | 0.54 | 0.56 | 0.53 | 0.55 |
| Regression Date/Time | 12/2/11 16:50 | 12/2/11 16:50 | 12/2/11 16:50 | 12/2/11 16:50 | 12/2/11 16:50 | 12/2/11 16:50 |
Definitions: Significance Levels: *** 1%, ** 5%, * 10%. FTE is defined as 2,000 man-hours.
Models: All models are ordinary least squares regressions; standard errors (shown in parentheses) are clustered at the mine level. The unit of analysis for all models is the mine-quarter.
Sample: public sample is: (1==1) (underground_mine==1) (coal_dummy==1) (bituminous==1) (active==1) (first_qtr_of_production==0) inrange(year, 1995, 2009). private sample is: (1==1) (underground_mine==1) (coal_dummy==1) (bituminous==1) (active==1) (first_qtr_of_production==0) inrange(year, 1998, 2009).
Independent Variables: All models include the following regressors: union dummy, union-size interaction term, mine size measure (defined as specified in column headers), logged controller size measure (defined as specified in column headers), mine age, productivity, number of lost-work injuries (in hundreds) in the previous four quarters, total penalty points (in thousands) in the previous four quarters, a constant term, dummies indicating presence of each type of mine subunit, quarter dummies, and district dummies. In addition: "Public Fields Only" models include the NIOSH longwall dummy; and "Confidential Fields" models include number of coal beds, mean coal bed thickness (in yards), subsidiary indicator, captive production as a percentage of total production, recoverable coal reserves, and mining method percentages.
Dependent Variable: the log of total proposed penalties per mine-quarter.