Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 15159 | Thousand metric tons | NA |
| 2004 | 16737 | Thousand metric tons | 10.41% |
| 2005 | 16202 | Thousand metric tons | -3.20% |
| 2006 | 16313 | Thousand metric tons | 0.69% |
| 2007 | 16300 | Thousand metric tons | -0.08% |
