| 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 | 0.182** | 0.274** | 0.240** | 0.360*** | 0.114 | 0.219** |
| (0.09) | (0.11) | (0.10) | (0.12) | (0.09) | (0.11) | |
| Union X Mine Size | -0.028 | -0.030 | -0.056* | -0.065** | -0.007 | -0.044 |
| (0.02) | (0.02) | (0.03) | (0.03) | (0.07) | (0.08) | |
| Mine Size | 0.010 | -0.016 | 0.018 | -0.003 | -0.036 | -0.126 |
| (0.03) | (0.03) | (0.03) | (0.04) | (0.07) | (0.08) | |
| Log of Controller Size | -0.038*** | -0.045*** | -0.040*** | -0.051*** | -0.028** | -0.035** |
| (0.01) | (0.02) | (0.01) | (0.02) | (0.01) | (0.01) | |
| Lost-Day Injuries in Prev. Year | -0.008** | -0.007** | -0.008** | -0.007** | -0.008*** | -0.008*** |
| (0.00) | (0.00) | (0.00) | (0.00) | (0.00) | (0.00) | |
| Penalty Pts. in Prev. Year | 0.003 | 0.004 | 0.003 | 0.003 | 0.004 | 0.003 |
| (0.00) | (0.00) | (0.00) | (0.00) | (0.00) | (0.00) | |
| Mine Age | 0.002 | -0.001 | 0.003 | -0.000 | 0.002 | -0.001 |
| (0.00) | (0.00) | (0.00) | (0.00) | (0.00) | (0.00) | |
| Productivity | -0.006 | -0.009* | -0.006 | -0.009* | -0.003 | -0.001 |
| (0.00) | (0.01) | (0.00) | (0.01) | (0.01) | (0.01) | |
| NIOSH Longwall Dummy | 0.218** | 0.223** | 0.235** | |||
| (0.09) | (0.09) | (0.09) | ||||
| Number of Coal Beds | 0.109 | 0.119 | 0.101 | |||
| (0.13) | (0.13) | (0.13) | ||||
| Avg. Coal Bed Thickness (yds.) | -0.071 | -0.077 | -0.077 | |||
| (0.05) | (0.05) | (0.05) | ||||
| Subsidiary Indicator | -0.005 | 0.001 | -0.001 | |||
| (0.06) | (0.06) | (0.06) | ||||
| Pct. Captive Production | -0.084 | -0.093 | -0.097 | |||
| (0.09) | (0.10) | (0.10) | ||||
| 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 | 0.015 | 0.065 | 0.022 | 0.071 | 0.012 | 0.064 |
| (0.11) | (0.11) | (0.11) | (0.11) | (0.11) | (0.11) | |
| Other Mining Subunit Dummy | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) |
| Strip/Quarry/Pit Subunit Dummy | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) |
| Surface at Underground Subunit | -0.082 | -0.071 | -0.074 | -0.057 | -0.075 | -0.060 |
| Dummy | (0.06) | (0.08) | (0.06) | (0.08) | (0.06) | (0.08) |
| Underground Subunit Dummy | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) |
| Pct. Continuous Mining Method | -0.001 | -0.002 | -0.002 | |||
| (0.00) | (0.00) | (0.00) | ||||
| Pct. Conventional Mining Method | -0.001 | -0.001 | -0.001 | |||
| (0.00) | (0.00) | (0.00) | ||||
| Pct. Longwall Mining Method | 0.004 | 0.003 | 0.003 | |||
| (0.00) | (0.00) | (0.00) | ||||
| Pct. Shortwall Mining Method | -0.011*** | -0.011*** | -0.012*** | |||
| (0.00) | (0.00) | (0.00) | ||||
| MSHA Coal District 1 Dummy | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) |
| MSHA Coal District 2 Dummy | -0.853*** | -0.853*** | -0.867*** | -0.866*** | -0.873*** | -0.875*** |
| (0.16) | (0.23) | (0.16) | (0.23) | (0.16) | (0.24) | |
| MSHA Coal District 3 Dummy | -1.443*** | -1.506*** | -1.434*** | -1.491*** | -1.481*** | -1.547*** |
| (0.15) | (0.21) | (0.15) | (0.21) | (0.15) | (0.22) | |
| MSHA Coal District 4 Dummy | -0.738*** | -0.777*** | -0.759*** | -0.799*** | -0.772*** | -0.835*** |
| (0.16) | (0.23) | (0.16) | (0.23) | (0.16) | (0.23) | |
| MSHA Coal District 5 Dummy | -0.550*** | -0.714*** | -0.561*** | -0.725*** | -0.565*** | -0.742*** |
| (0.17) | (0.23) | (0.17) | (0.23) | (0.17) | (0.23) | |
| MSHA Coal District 6 Dummy | -0.794*** | -0.835*** | -0.803*** | -0.841*** | -0.830*** | -0.886*** |
| (0.16) | (0.22) | (0.16) | (0.22) | (0.16) | (0.23) | |
| MSHA Coal District 7 Dummy | -1.199*** | -1.196*** | -1.194*** | -1.192*** | -1.217*** | -1.229*** |
| (0.16) | (0.22) | (0.16) | (0.21) | (0.16) | (0.22) | |
| MSHA Coal District 8 Dummy | -0.796*** | -0.754*** | -0.815*** | -0.774*** | -0.779*** | -0.766*** |
| (0.20) | (0.24) | (0.19) | (0.23) | (0.19) | (0.24) | |
| MSHA Coal District 9 Dummy | (dropped) | 0.177 | (dropped) | 0.183 | (dropped) | 0.165 |
| (0.28) | (0.27) | (0.28) | ||||
| MSHA Coal District 10 Dummy | -0.195 | (dropped) | -0.189 | (dropped) | -0.179 | (dropped) |
| (0.25) | (0.25) | (0.26) | ||||
| MSHA Coal District 11 Dummy | -0.855*** | -0.935*** | -0.834*** | -0.921*** | -0.914*** | -1.060*** |
| (0.23) | (0.25) | (0.22) | (0.25) | (0.22) | (0.26) | |
| MSHA Coal District 12 Dummy | -0.763*** | -0.788*** | -0.763*** | -0.785*** | -0.769*** | -0.814*** |
| (0.16) | (0.23) | (0.16) | (0.23) | (0.16) | (0.23) | |
| MSHA Coal District 13 Dummy | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) | (dropped) |
| 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 | 0.029 | (dropped) | 0.209* | (dropped) | 0.210* | (dropped) |
| (0.12) | (0.11) | (0.11) | ||||
| Quarter Dummy - 1995q2 | -0.055 | (dropped) | 0.118 | (dropped) | 0.119 | (dropped) |
| (0.13) | (0.12) | (0.12) | ||||
| Quarter Dummy - 1995q3 | -0.014 | (dropped) | 0.185* | (dropped) | 0.181* | (dropped) |
| (0.11) | (0.10) | (0.10) | ||||
| Quarter Dummy - 1995q4 | -0.036 | (dropped) | 0.149 | (dropped) | 0.150 | (dropped) |
| (0.11) | (0.11) | (0.11) | ||||
| Quarter Dummy - 1996q1 | -0.097 | (dropped) | 0.086 | (dropped) | 0.088 | (dropped) |
| (0.11) | (0.10) | (0.10) | ||||
| Quarter Dummy - 1996q2 | -0.073 | (dropped) | 0.110 | (dropped) | 0.109 | (dropped) |
| (0.11) | (0.09) | (0.09) | ||||
| Quarter Dummy - 1996q3 | -0.074 | (dropped) | 0.126 | (dropped) | 0.126 | (dropped) |
| (0.11) | (0.09) | (0.09) | ||||
| Quarter Dummy - 1996q4 | -0.170 | (dropped) | 0.011 | (dropped) | 0.005 | (dropped) |
| (0.12) | (0.10) | (0.10) | ||||
| Quarter Dummy - 1997q1 | -0.171 | (dropped) | -0.021 | (dropped) | -0.023 | (dropped) |
| (0.11) | (0.10) | (0.10) | ||||
| Quarter Dummy - 1997q2 | -0.158 | (dropped) | 0.036 | (dropped) | 0.036 | (dropped) |
| (0.11) | (0.11) | (0.11) | ||||
| Quarter Dummy - 1997q3 | -0.217** | (dropped) | -0.033 | (dropped) | -0.033 | (dropped) |
| (0.11) | (0.09) | (0.09) | ||||
| Quarter Dummy - 1997q4 | -0.144 | (dropped) | 0.038 | (dropped) | 0.039 | (dropped) |
| (0.12) | (0.10) | (0.10) | ||||
| Quarter Dummy - 1998q1 | -0.093 | 0.067 | 0.086 | 0.069 | 0.087 | 0.071 |
| (0.13) | (0.10) | (0.12) | (0.10) | (0.12) | (0.10) | |
| Quarter Dummy - 1998q2 | -0.150 | (dropped) | 0.025 | (dropped) | 0.027 | (dropped) |
| (0.12) | (0.11) | (0.11) | ||||
| Quarter Dummy - 1998q3 | -0.117 | 0.019 | 0.025 | -0.005 | 0.023 | -0.013 |
| (0.12) | (0.10) | (0.10) | (0.10) | (0.10) | (0.10) | |
| Quarter Dummy - 1998q4 | -0.151 | -0.007 | 0.020 | -0.010 | 0.023 | -0.008 |
| (0.12) | (0.10) | (0.10) | (0.10) | (0.10) | (0.10) | |
| Quarter Dummy - 1999q1 | -0.179 | 0.050 | 0.007 | 0.071 | 0.007 | 0.073 |
| (0.12) | (0.13) | (0.11) | (0.13) | (0.11) | (0.13) | |
| Quarter Dummy - 1999q2 | -0.206* | 0.017 | -0.057 | -0.001 | -0.057 | -0.003 |
| (0.12) | (0.12) | (0.11) | (0.12) | (0.11) | (0.13) | |
| Quarter Dummy - 1999q3 | -0.293*** | -0.074 | -0.118 | -0.062 | -0.118 | -0.065 |
| (0.11) | (0.12) | (0.09) | (0.12) | (0.09) | (0.12) | |
| Quarter Dummy - 1999q4 | -0.183 | 0.051 | -0.003 | 0.067 | -0.003 | 0.063 |
| (0.12) | (0.13) | (0.11) | (0.13) | (0.11) | (0.13) | |
| Quarter Dummy - 2000q1 | -0.222** | 0.004 | -0.047 | 0.013 | -0.043 | 0.017 |
| (0.11) | (0.12) | (0.10) | (0.12) | (0.10) | (0.12) | |
| Quarter Dummy - 2000q2 | -0.076 | 0.161 | 0.115 | 0.190 | 0.118 | 0.192 |
| (0.12) | (0.13) | (0.11) | (0.13) | (0.11) | (0.13) | |
| Quarter Dummy - 2000q3 | -0.020 | 0.223 | 0.164 | 0.248* | 0.161 | 0.243* |
| (0.13) | (0.14) | (0.12) | (0.14) | (0.12) | (0.14) | |
| Quarter Dummy - 2000q4 | -0.149 | 0.102 | -0.058 | 0.028 | -0.058 | 0.027 |
| (0.14) | (0.15) | (0.10) | (0.13) | (0.10) | (0.13) | |
| Quarter Dummy - 2001q1 | -0.159 | 0.088 | 0.030 | 0.112 | 0.028 | 0.110 |
| (0.11) | (0.12) | (0.10) | (0.12) | (0.10) | (0.12) | |
| Quarter Dummy - 2001q2 | -0.112 | 0.132 | 0.073 | 0.153 | 0.068 | 0.145 |
| (0.11) | (0.12) | (0.10) | (0.12) | (0.10) | (0.12) | |
| Quarter Dummy - 2001q3 | -0.201* | 0.052 | -0.021 | 0.072 | -0.027 | 0.058 |
| (0.11) | (0.12) | (0.10) | (0.13) | (0.10) | (0.12) | |
| Quarter Dummy - 2001q4 | -0.188* | 0.060 | -0.002 | 0.085 | -0.007 | 0.076 |
| (0.11) | (0.13) | (0.09) | (0.14) | (0.09) | (0.13) | |
| Quarter Dummy - 2002q1 | -0.140 | 0.100 | 0.036 | 0.115 | 0.032 | 0.110 |
| (0.11) | (0.13) | (0.08) | (0.13) | (0.08) | (0.13) | |
| Quarter Dummy - 2002q2 | -0.175* | 0.061 | (dropped) | 0.075 | (dropped) | 0.070 |
| (0.10) | (0.13) | (0.13) | (0.13) | |||
| Quarter Dummy - 2002q3 | -0.067 | 0.171 | 0.108 | 0.185 | 0.105 | 0.173 |
| (0.11) | (0.13) | (0.08) | (0.13) | (0.08) | (0.13) | |
| Quarter Dummy - 2002q4 | (dropped) | 0.236* | 0.191* | 0.266* | 0.191* | 0.263* |
| (0.14) | (0.10) | (0.14) | (0.10) | (0.14) | ||
| Quarter Dummy - 2003q1 | 0.292** | 0.527*** | 0.494*** | 0.564*** | 0.496*** | 0.563*** |
| (0.12) | (0.15) | (0.12) | (0.15) | (0.11) | (0.15) | |
| Quarter Dummy - 2003q2 | 0.413*** | 0.661*** | 0.593*** | 0.677*** | 0.598*** | 0.682*** |
| (0.15) | (0.15) | (0.13) | (0.16) | (0.13) | (0.15) | |
| Quarter Dummy - 2003q3 | 0.259** | 0.504*** | 0.430*** | 0.511*** | 0.435*** | 0.512*** |
| (0.11) | (0.13) | (0.11) | (0.13) | (0.11) | (0.13) | |
| Quarter Dummy - 2003q4 | 0.187* | 0.435*** | 0.358*** | 0.444*** | 0.360*** | 0.445*** |
| (0.11) | (0.13) | (0.10) | (0.13) | (0.10) | (0.13) | |
| Quarter Dummy - 2004q1 | 0.147 | 0.391*** | 0.324*** | 0.400*** | 0.328*** | 0.409*** |
| (0.12) | (0.15) | (0.11) | (0.15) | (0.11) | (0.15) | |
| Quarter Dummy - 2004q2 | 0.096 | 0.348*** | 0.263*** | 0.354*** | 0.263*** | 0.350*** |
| (0.11) | (0.13) | (0.09) | (0.13) | (0.09) | (0.13) | |
| Quarter Dummy - 2004q3 | 0.198* | 0.455*** | 0.400*** | 0.495*** | 0.398*** | 0.489*** |
| (0.11) | (0.14) | (0.10) | (0.14) | (0.10) | (0.14) | |
| Quarter Dummy - 2004q4 | 0.235* | 0.482*** | 0.413*** | 0.496*** | 0.412*** | 0.500*** |
| (0.13) | (0.13) | (0.11) | (0.13) | (0.11) | (0.13) | |
| Quarter Dummy - 2005q1 | 0.056 | 0.311*** | 0.237** | 0.325*** | 0.239** | 0.330*** |
| (0.10) | (0.12) | (0.09) | (0.12) | (0.09) | (0.12) | |
| Quarter Dummy - 2005q2 | -0.056 | 0.207 | 0.126 | 0.220* | 0.126 | 0.222* |
| (0.10) | (0.13) | (0.09) | (0.13) | (0.09) | (0.13) | |
| Quarter Dummy - 2005q3 | 0.092 | 0.352*** | 0.275*** | 0.372*** | 0.272*** | 0.371*** |
| (0.11) | (0.12) | (0.09) | (0.13) | (0.09) | (0.13) | |
| Quarter Dummy - 2005q4 | 0.087 | 0.347*** | 0.265** | 0.362*** | 0.258** | 0.352*** |
| (0.12) | (0.13) | (0.10) | (0.14) | (0.10) | (0.14) | |
| Quarter Dummy - 2006q1 | 0.263** | 0.508*** | 0.443*** | 0.523*** | 0.438*** | 0.519*** |
| (0.12) | (0.13) | (0.10) | (0.14) | (0.10) | (0.14) | |
| Quarter Dummy - 2006q2 | 0.462*** | 0.717*** | 0.647*** | 0.742*** | 0.642*** | 0.737*** |
| (0.11) | (0.13) | (0.11) | (0.13) | (0.11) | (0.13) | |
| Quarter Dummy - 2006q3 | 0.506*** | 0.755*** | 0.676*** | 0.765*** | 0.669*** | 0.753*** |
| (0.13) | (0.14) | (0.11) | (0.14) | (0.11) | (0.14) | |
| Quarter Dummy - 2006q4 | 0.386*** | 0.649*** | 0.563*** | 0.665*** | 0.558*** | 0.657*** |
| (0.11) | (0.12) | (0.10) | (0.13) | (0.10) | (0.13) | |
| Quarter Dummy - 2007q1 | 0.270** | 0.535*** | 0.443*** | 0.542*** | 0.444*** | 0.545*** |
| (0.11) | (0.13) | (0.10) | (0.13) | (0.10) | (0.13) | |
| Quarter Dummy - 2007q2 | 0.937*** | 1.194*** | 1.118*** | 1.212*** | 1.113*** | 1.200*** |
| (0.17) | (0.18) | (0.16) | (0.18) | (0.16) | (0.18) | |
| Quarter Dummy - 2007q3 | 1.244*** | 1.508*** | 1.423*** | 1.526*** | 1.417*** | 1.513*** |
| (0.18) | (0.19) | (0.19) | (0.20) | (0.19) | (0.20) | |
| Quarter Dummy - 2007q4 | 1.494*** | 1.746*** | 1.657*** | 1.751*** | 1.648*** | 1.739*** |
| (0.15) | (0.16) | (0.15) | (0.16) | (0.15) | (0.16) | |
| Quarter Dummy - 2008q1 | 0.900*** | 1.163*** | 1.072*** | 1.170*** | 1.063*** | 1.166*** |
| (0.18) | (0.20) | (0.17) | (0.20) | (0.17) | (0.20) | |
| Quarter Dummy - 2008q2 | 0.888*** | 1.152*** | 1.073*** | 1.174*** | 1.059*** | 1.164*** |
| (0.16) | (0.18) | (0.16) | (0.18) | (0.16) | (0.18) | |
| Quarter Dummy - 2008q3 | 1.191*** | 1.457*** | 1.351*** | 1.456*** | 1.335*** | 1.441*** |
| (0.16) | (0.18) | (0.16) | (0.18) | (0.16) | (0.18) | |
| Quarter Dummy - 2008q4 | 1.224*** | 1.480*** | 1.415*** | 1.512*** | 1.400*** | 1.502*** |
| (0.21) | (0.23) | (0.20) | (0.23) | (0.20) | (0.23) | |
| Quarter Dummy - 2009q1 | 1.079*** | 1.287*** | 1.254*** | 1.300*** | 1.241*** | 1.288*** |
| (0.18) | (0.20) | (0.17) | (0.20) | (0.17) | (0.20) | |
| Quarter Dummy - 2009q2 | 0.884*** | 1.102*** | 1.105*** | 1.162*** | 1.088*** | 1.144*** |
| (0.16) | (0.18) | (0.16) | (0.18) | (0.16) | (0.18) | |
| Quarter Dummy - 2009q3 | 1.036*** | 1.251*** | 1.227*** | 1.283*** | 1.208*** | 1.264*** |
| (0.17) | (0.19) | (0.17) | (0.19) | (0.17) | (0.19) | |
| Quarter Dummy - 2009q4 | 0.722*** | 0.942*** | 0.884*** | 0.948*** | 0.862*** | 0.930*** |
| (0.15) | (0.16) | (0.14) | (0.16) | (0.14) | (0.16) | |
| I_v_cfr_sec_1 | 0.742*** | 0.867*** | 0.750*** | 0.875*** | 0.746*** | 0.878*** |
| (0.10) | (0.10) | (0.08) | (0.12) | (0.08) | (0.12) | |
| I_v_cfr_sec_2 | 0.152** | 0.192*** | 0.158*** | 0.201** | 0.151*** | 0.199** |
| (0.08) | (0.07) | (0.06) | (0.09) | (0.06) | (0.09) | |
| I_v_cfr_sec_3 | 0.443*** | 0.508*** | 0.447*** | 0.511*** | 0.439*** | 0.509*** |
| (0.09) | (0.08) | (0.07) | (0.10) | (0.07) | (0.10) | |
| I_v_cfr_sec_4 | 2.092*** | 2.327*** | 2.104*** | 2.338*** | 2.100*** | 2.341*** |
| (0.10) | (0.10) | (0.09) | (0.12) | (0.09) | (0.12) | |
| I_v_cfr_sec_5 | 1.406*** | 1.510*** | 1.407*** | 1.511*** | 1.404*** | 1.515*** |
| (0.11) | (0.10) | (0.09) | (0.12) | (0.09) | (0.12) | |
| I_v_cfr_sec_6 | 0.746*** | 0.805*** | 0.748*** | 0.807*** | 0.745*** | 0.812*** |
| (0.09) | (0.08) | (0.07) | (0.10) | (0.07) | (0.10) | |
| I_v_cfr_sec_7 | 0.061 | 0.100 | 0.066 | 0.106 | 0.060 | 0.108 |
| (0.08) | (0.07) | (0.06) | (0.09) | (0.06) | (0.09) | |
| I_v_cfr_sec_8 | -0.170** | -0.162** | -0.167*** | -0.157* | -0.172*** | -0.157* |
| (0.08) | (0.07) | (0.06) | (0.09) | (0.06) | (0.09) | |
| I_v_cfr_sec_9 | -0.004 | (dropped) | (dropped) | 0.006 | (dropped) | 0.011 |
| (0.08) | (0.09) | (0.09) | ||||
| I_v_cfr_sec_10 | (dropped) | -0.008 | 0.007 | (dropped) | 0.002 | (dropped) |
| (0.09) | (0.08) | (0.08) | ||||
| Constant | 1.838*** | 1.699*** | 1.648*** | 1.693*** | 1.617*** | 1.651*** |
| (0.21) | (0.35) | (0.20) | (0.36) | (0.20) | (0.37) | |
| Observations | 106,483 | 83,968 | 104,030 | 82,081 | 104,030 | 82,081 |
| # of Union Mines / # of Total Mines | 226 / 1,547 | 150 / 1,134 | 225 / 1,540 | 150 / 1,129 | 225 / 1,540 | 150 / 1,129 |
| R2 | 0.12 | 0.12 | 0.12 | 0.12 | 0.12 | 0.12 |
| Regression Date/Time | 12/2/11 22:28 | 12/2/11 22:28 | 12/2/11 22:28 | 12/2/11 22:29 | 12/2/11 22:29 | 12/2/11 22:29 |
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 s&s violation
10 most common violation types
".Sample: public sample is: (sig_or_sub==1) (ten_most_common_violation==1) (violator_contractor==0) (underground_mine==1) (coal_dummy==1) (bituminous==1) (active==1) (first_qtr_of_production==0) inrange(year, 1995, 2009). private sample is: (sig_or_sub==1) (ten_most_common_violation==1) (violator_contractor==0) (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, district dummies, and dummies for each violation type (i.e., section of CFR deemed to have been violated. 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 number of penalty points assigned due to the number of persons that could be affected per S&S violation (limited to ten most common violation types).