Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 164140 | Metric tons, gross weight | NA |
| 2003 | 204339 | Metric tons, gross weight | 24.49% |
| 2004 | 216277 | Metric tons, gross weight | 5.84% |
| 2005 | 197653 | Metric tons, gross weight | -8.61% |
| 2006 | 200000 | Metric tons, gross weight | 1.19% |
