Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 830 | Thousand metric tons | NA |
| 2004 | 835 | Thousand metric tons | 0.60% |
| 2005 | 830 | Thousand metric tons | -0.60% |
| 2006 | 850 | Thousand metric tons | 2.41% |
| 2007 | 850 | Thousand metric tons | 0.00% |
