Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 4709 | Thousand metric tons | NA |
| 2004 | 4564 | Thousand metric tons | -3.08% |
| 2005 | 4242 | Thousand metric tons | -7.06% |
| 2006 | 4847.56201171875 | Thousand metric tons | 14.28% |
| 2007 | 4800.27685546875 | Thousand metric tons | -0.98% |
