Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 294871 | Metric tons | NA |
| 2004 | 222826 | Metric tons | -24.43% |
| 2005 | 223000 | Metric tons | 0.08% |
| 2006 | 223000 | Metric tons | 0.00% |
| 2007 | 223000 | Metric tons | 0.00% |
| 2008 | 223000 | Metric tons | 0.00% |
| 2009 | 200000 | Metric tons | -10.31% |
