Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 74000 | Metric tons | NA |
| 2004 | 75000 | Metric tons | 1.35 % |
| 2005 | 76000 | Metric tons | 1.33 % |
| 2006 | 75000 | Metric tons | -1.32 % |
| 2007 | 75000 | Metric tons | 0.00 % |
| 2008 | 75000 | Metric tons | 0.00 % |
