Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 350000 | Metric tons | NA |
| 2004 | 178000 | Metric tons | -49.14% |
| 2005 | 357000 | Metric tons | 100.56% |
| 2006 | 360000 | Metric tons | 0.84% |
| 2007 | 360000 | Metric tons | 0.00% |
| 2008 | 360000 | Metric tons | 0.00% |
