Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 6500 | Thousand metric tons | NA |
| 2004 | 5062.8818359375 | Thousand metric tons | -22.11 % |
| 2005 | 5100 | Thousand metric tons | 0.73 % |
| 2006 | 5100 | Thousand metric tons | 0.00 % |
| 2007 | 5000 | Thousand metric tons | -1.96 % |
| 2008 | 5000 | Thousand metric tons | 0.00 % |
| 2009 | 5000 | Thousand metric tons | 0.00 % |