Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 291.35400390625 | Thousand metric tons | NA |
| 2004 | 315 | Thousand metric tons | 8.12% |
| 2005 | 321.170013427734 | Thousand metric tons | 1.96% |
| 2006 | 326.484008789063 | Thousand metric tons | 1.65% |
| 2007 | 359 | Thousand metric tons | 9.96% |
