Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 1178 | Thousand metric tons | NA |
| 2003 | 1370 | Thousand metric tons | 16.30% |
| 2004 | 1186 | Thousand metric tons | -13.43% |
| 2005 | 1114 | Thousand metric tons | -6.07% |
| 2006 | 1269 | Thousand metric tons | 13.91% |
| 2007 | 1300 | Thousand metric tons | 2.44% |
| 2008 | 1525 | Thousand metric tons | 17.31% |
| 2009 | 1082 | Thousand metric tons | -29.05% |
| 2010 | 799 | Thousand metric tons | -26.16% |
| 2011 | 620 | Thousand metric tons | -22.40% |
| 2012 | 1000 | Thousand metric tons | 61.29% |
