Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 299000 | Metric tons, gross weight | NA |
| 2003 | 438000 | Metric tons, gross weight | 46.49% |
| 2004 | 508000 | Metric tons, gross weight | 15.98% |
| 2005 | 480000 | Metric tons, gross weight | -5.51% |
| 2006 | 573000 | Metric tons, gross weight | 19.38% |
