Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 4.19999980926514 | Thousand metric tons | NA |
| 2004 | 4.19999980926514 | Thousand metric tons | 0.00% |
| 2005 | 4.30000019073486 | Thousand metric tons | 2.38% |
| 2006 | 4.19999980926514 | Thousand metric tons | -2.33% |
| 2007 | 4.19999980926514 | Thousand metric tons | 0.00% |
| 2008 | 4.19999980926514 | Thousand metric tons | 0.00% |
| 2009 | 4 | Thousand metric tons | -4.76% |
