Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 14770 | Metric tons | NA |
| 2004 | 15500 | Metric tons | 4.94% |
| 2005 | 15750 | Metric tons | 1.61% |
| 2006 | 14864 | Metric tons | -5.63% |
| 2007 | 15000 | Metric tons | 0.91% |
