Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 258164 | Metric tons, gross weight | NA |
| 2003 | 245200 | Metric tons, gross weight | -5.02% |
| 2004 | 193077 | Metric tons, gross weight | -21.26% |
| 2005 | 235000 | Metric tons, gross weight | 21.71% |
| 2006 | 200000 | Metric tons, gross weight | -14.89% |
