Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 232000 | Metric tons, gross weight | NA |
| 2003 | 184000 | Metric tons, gross weight | -20.69% |
| 2004 | 251000 | Metric tons, gross weight | 36.41% |
| 2005 | 253000 | Metric tons, gross weight | 0.80% |
| 2006 | 295000 | Metric tons, gross weight | 16.60% |
