Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 24 | Thousand metric tons | NA |
| 2004 | 25 | Thousand metric tons | 4.17% |
| 2005 | 26 | Thousand metric tons | 4.00% |
| 2006 | 26.5 | Thousand metric tons | 1.92% |
| 2007 | 26.5 | Thousand metric tons | 0.00% |
| 2008 | 26.5 | Thousand metric tons | 0.00% |
| 2009 | 26 | Thousand metric tons | -1.89% |
