Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 50000 | Metric tons | NA |
| 2004 | 46000 | Metric tons | -8.00% |
| 2005 | 45000 | Metric tons | -2.17% |
| 2006 | 42422 | Metric tons | -5.73% |
| 2007 | 42000 | Metric tons | -0.99% |
