Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 36900 | Metric tons | NA |
| 2003 | 26400 | Metric tons | -28.46% |
| 2004 | 24000 | Metric tons | -9.09% |
| 2005 | 26100 | Metric tons | 8.75% |
| 2006 | 25100 | Metric tons | -3.83% |
