Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 381100 | Metric tons | NA |
| 2004 | 400000 | Metric tons | 4.96% |
| 2005 | 400000 | Metric tons | 0.00% |
| 2006 | 400000 | Metric tons | 0.00% |
| 2007 | 400000 | Metric tons | 0.00% |
