Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 9678 | Thousand metric tons | NA |
| 2004 | 8353 | Thousand metric tons | -13.69% |
| 2005 | 7788 | Thousand metric tons | -6.76% |
| 2006 | 7937 | Thousand metric tons | 1.91% |
| 2007 | 8047 | Thousand metric tons | 1.39% |
