Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 6261 | Thousand metric tons | NA |
| 2004 | 6530 | Thousand metric tons | 4.30% |
| 2005 | 7031 | Thousand metric tons | 7.67% |
| 2006 | 6487 | Thousand metric tons | -7.74% |
| 2007 | 6871 | Thousand metric tons | 5.92% |
