Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 315000 | Metric tons, gross weight | NA |
| 2003 | 325000 | Metric tons, gross weight | 3.17% |
| 2004 | 330000 | Metric tons, gross weight | 1.54% |
| 2005 | 340000 | Metric tons, gross weight | 3.03% |
| 2006 | 360000 | Metric tons, gross weight | 5.88% |
