Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 266100 | Kilograms | NA |
| 2003 | 282000 | Kilograms | 5.98% |
| 2004 | 259000 | Kilograms | -8.16% |
| 2005 | 262000 | Kilograms | 1.16% |
| 2006 | 247000 | Kilograms | -5.73% |
| 2007 | 247000 | Kilograms | 0.00% |
| 2008 | 215000 | Kilograms | -12.96% |
| 2009 | 224000 | Kilograms | 4.19% |
| 2010 | 261000 | Kilograms | 16.52% |
| 2011 | 260000 | Kilograms | -0.38% |
| 2012 | 250000 | Kilograms | -3.85% |
