Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 506 | Thousand metric tons | NA |
| 2003 | 507 | Thousand metric tons | 0.20 % |
| 2004 | 558.987976074219 | Thousand metric tons | 10.25 % |
| 2005 | 630 | Thousand metric tons | 12.70 % |
| 2006 | 630 | Thousand metric tons | 0.00 % |
| 2007 | 650 | Thousand metric tons | 3.17 % |
| 2008 | 650 | Thousand metric tons | 0.00 % |
