Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 500 | Thousand metric tons | NA |
| 2004 | 400 | Thousand metric tons | -20.00% |
| 2005 | 470 | Thousand metric tons | 17.50% |
| 2006 | 558 | Thousand metric tons | 18.72% |
| 2007 | 590 | Thousand metric tons | 5.73% |
