Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 96000 | Kilograms | NA |
| 2003 | 97000 | Kilograms | 1.04% |
| 2004 | 97000 | Kilograms | 0.00% |
| 2005 | 97400 | Kilograms | 0.41% |
| 2006 | 98400 | Kilograms | 1.03% |
| 2007 | 96800 | Kilograms | -1.63% |
| 2008 | 87700 | Kilograms | -9.40% |
| 2009 | 83200 | Kilograms | -5.13% |
