| 年份 | 分类 | 数值 |
| 2007 | United States : coal dollars per tons | 41.14 |
| 2008 | United States : coal dollars per tons | 43.74 |
| 2009 | United States : coal dollars per tons | 44.64 |
| 2010 | United States : coal dollars per tons | NA |
| 2011 | United States : coal dollars per tons | NA |
| 2012 | United States : coal dollars per tons | NA |
| 2013 | United States : coal dollars per tons | NA |
| 2014 | United States : coal dollars per tons | NA |