Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 641 | Thousand metric tons | NA |
| 2004 | 555 | Thousand metric tons | -13.42% |
| 2005 | 475 | Thousand metric tons | -14.41% |
| 2006 | 522 | Thousand metric tons | 9.89% |
| 2007 | 520 | Thousand metric tons | -0.38% |
| 2008 | 520 | Thousand metric tons | 0.00% |
| 2009 | 520 | Thousand metric tons | 0.00% |
