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 | 212571 | Kilograms | -15.85% |
| 2009 | 197628 | Kilograms | -7.03% |
| 2010 | 188702 | Kilograms | -4.52% |
| 2011 | 180184 | Kilograms | -4.51% |
| 2012 | 160000 | Kilograms | -11.20% |
