Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 398523 | Kilograms | NA |
| 2003 | 373300 | Kilograms | -6.33 % |
| 2004 | 337223 | Kilograms | -9.66 % |
| 2005 | 294671 | Kilograms | -12.62 % |
| 2006 | 272128 | Kilograms | -7.65 % |
| 2007 | 252598 | Kilograms | -7.18 % |
| 2008 | 212744 | Kilograms | -15.78 % |
| 2009 | 197698 | Kilograms | -7.07 % |
