Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 5111 | Thousand metric tons | NA |
| 2004 | 5300 | Thousand metric tons | 3.70% |
| 2005 | 5300 | Thousand metric tons | 0.00% |
| 2006 | 6793 | Thousand metric tons | 28.17% |
| 2007 | 6890 | Thousand metric tons | 1.43% |
