Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 250000 | Metric tons, gross weight | NA |
| 2003 | 250000 | Metric tons, gross weight | 0.00% |
| 2004 | 250000 | Metric tons, gross weight | 0.00% |
| 2005 | 260000 | Metric tons, gross weight | 4.00% |
| 2006 | 265000 | Metric tons, gross weight | 1.92% |
