Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1090 | Thousand metric tons | NA |
| 2004 | 1070 | Thousand metric tons | -1.83% |
| 2005 | 1070 | Thousand metric tons | 0.00% |
| 2006 | 1180 | Thousand metric tons | 10.28% |
| 2007 | 1230 | Thousand metric tons | 4.24% |
