Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 1200 | Thousand metric tons | NA |
| 2003 | 1600 | Thousand metric tons | 33.33 % |
| 2004 | 1500 | Thousand metric tons | -6.25 % |
| 2005 | 1400 | Thousand metric tons | -6.67 % |
| 2006 | 1399.78894042969 | Thousand metric tons | -0.02 % |
| 2007 | 1400 | Thousand metric tons | 0.02 % |
| 2008 | 1400 | Thousand metric tons | 0.00 % |
