Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 5500 | Thousand metric tons | NA |
| 2004 | 6000 | Thousand metric tons | 9.09% |
| 2005 | 5000 | Thousand metric tons | -16.67% |
| 2006 | 6300 | Thousand metric tons | 26.00% |
| 2007 | 5775 | Thousand metric tons | -8.33% |
| 2008 | 5675 | Thousand metric tons | -1.73% |
| 2009 | 5775 | Thousand metric tons | 1.76% |
