Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 38688 | Kilograms | NA |
| 2003 | 38954 | Kilograms | 0.69 % |
| 2004 | 39986 | Kilograms | 2.65 % |
| 2005 | 40447 | Kilograms | 1.15 % |
| 2006 | 42100 | Kilograms | 4.09 % |
| 2007 | 41527 | Kilograms | -1.36 % |
| 2008 | 39162 | Kilograms | -5.70 % |
| 2009 | 40834 | Kilograms | 4.27 % |
