Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 15700 | Kilograms | NA |
| 2003 | 20100 | Kilograms | 28.03% |
| 2004 | 21300 | Kilograms | 5.97% |
| 2005 | 21500 | Kilograms | 0.94% |
| 2006 | 19800 | Kilograms | -7.91% |
| 2007 | 22900 | Kilograms | 15.66% |
| 2008 | 27600 | Kilograms | 20.52% |
| 2009 | 25000 | Kilograms | -9.42% |
| 2010 | 25000 | Kilograms | 0.00% |
| 2011 | 24000 | Kilograms | -4.00% |
| 2012 | 27000 | Kilograms | 12.50% |
| 2013 | 25000 | Kilograms | -7.41% |
