Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 9073 | Metric tons | NA |
| 2004 | 9200 | Metric tons | 1.40% |
| 2005 | 9400 | Metric tons | 2.17% |
| 2006 | 9500 | Metric tons | 1.06% |
| 2007 | 9500 | Metric tons | 0.00% |
