Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 1631 | Thousand metric tons | NA |
| 2003 | 1650 | Thousand metric tons | 1.16 % |
| 2004 | 1420 | Thousand metric tons | -13.94 % |
| 2005 | 1613 | Thousand metric tons | 13.59 % |
| 2006 | 1695 | Thousand metric tons | 5.08 % |
| 2007 | 1700 | Thousand metric tons | 0.29 % |
| 2008 | 1700 | Thousand metric tons | 0.00 % |
