Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 83 | Thousand metric tons | NA |
| 2003 | 90 | Thousand metric tons | 8.43 % |
| 2004 | 100.287002563477 | Thousand metric tons | 11.43 % |
| 2005 | 132.438003540039 | Thousand metric tons | 32.06 % |
| 2006 | 141.432998657227 | Thousand metric tons | 6.79 % |
| 2007 | 90 | Thousand metric tons | -36.37 % |
| 2008 | 138 | Thousand metric tons | 53.33 % |
| 2009 | 138 | Thousand metric tons | 0.00 % |
| 2010 | 140 | Thousand metric tons | 1.45 % |
| 2011 | 140 | Thousand metric tons | 0.00 % |
| 2012 | 140 | Thousand metric tons | 0.00 % |
