Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 9481 | Thousand metric tons | NA |
| 2004 | 9500 | Thousand metric tons | 0.20% |
| 2005 | 9494 | Thousand metric tons | -0.06% |
| 2006 | 9718 | Thousand metric tons | 2.36% |
| 2007 | 9100 | Thousand metric tons | -6.36% |
