Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 8200 | Metric tons | NA |
| 2004 | 8300 | Metric tons | 1.22% |
| 2005 | 8400 | Metric tons | 1.20% |
| 2006 | 8500 | Metric tons | 1.19% |
| 2007 | 8600 | Metric tons | 1.18% |
