Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 3572 | Thousand metric tons | NA |
| 2004 | 4533 | Thousand metric tons | 26.90% |
| 2005 | 5161 | Thousand metric tons | 13.85% |
| 2006 | 5210 | Thousand metric tons | 0.95% |
| 2007 | 5470 | Thousand metric tons | 4.99% |
