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% |
| 2010 | 39494 | Kilograms | -3.28% |
| 2011 | 45137 | Kilograms | 14.29% |
| 2012 | 49936 | Kilograms | 10.63% |
