Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 6783 | Thousand metric tons | NA |
| 2004 | 7033 | Thousand metric tons | 3.69% |
| 2005 | 6189 | Thousand metric tons | -12.00% |
| 2006 | 6862 | Thousand metric tons | 10.87% |
| 2007 | 7059 | Thousand metric tons | 2.87% |
