Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 31281 | Metric tons | NA |
| 2004 | 23000 | Metric tons | -26.47% |
| 2005 | 20988 | Metric tons | -8.75% |
| 2006 | 17157 | Metric tons | -18.25% |
| 2007 | 15085 | Metric tons | -12.08% |
| 2008 | 15000 | Metric tons | -0.56% |
| 2009 | 15000 | Metric tons | 0.00% |
