Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 4860 | Thousand metric tons | NA |
| 2004 | 5350 | Thousand metric tons | 10.08% |
| 2005 | 5220 | Thousand metric tons | -2.43% |
| 2006 | 4700 | Thousand metric tons | -9.96% |
| 2007 | 3900 | Thousand metric tons | -17.02% |
