Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 2000 | Thousand metric tons | NA |
| 2003 | 2000 | Thousand metric tons | 0.00 % |
| 2004 | 2200 | Thousand metric tons | 10.00 % |
| 2005 | 2400 | Thousand metric tons | 9.09 % |
| 2006 | 2500 | Thousand metric tons | 4.17 % |
| 2007 | 2500 | Thousand metric tons | 0.00 % |
| 2008 | 2500 | Thousand metric tons | 0.00 % |
