Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 135 | Thousand metric tons | NA |
| 2004 | 140 | Thousand metric tons | 3.70% |
| 2005 | 150 | Thousand metric tons | 7.14% |
| 2006 | 150 | Thousand metric tons | 0.00% |
| 2007 | 150 | Thousand metric tons | 0.00% |
