Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 226.156005859375 | Thousand metric tons | NA |
| 2004 | 232 | Thousand metric tons | 2.58% |
| 2005 | 207 | Thousand metric tons | -10.78% |
| 2006 | 292 | Thousand metric tons | 41.06% |
| 2007 | 349 | Thousand metric tons | 19.52% |
