Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 41000 | Metric tons | NA |
| 2004 | 42000 | Metric tons | 2.44% |
| 2005 | 43000 | Metric tons | 2.38% |
| 2006 | 42000 | Metric tons | -2.33% |
| 2007 | 42000 | Metric tons | 0.00% |
| 2008 | 42000 | Metric tons | 0.00% |
