Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 4766 | Thousand metric tons | NA |
| 2004 | 4833 | Thousand metric tons | 1.41% |
| 2005 | 4738 | Thousand metric tons | -1.97% |
| 2006 | 5052 | Thousand metric tons | 6.63% |
| 2007 | 5000 | Thousand metric tons | -1.03% |
