Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 298000 | Kilograms | NA |
| 2003 | 277000 | Kilograms | -7.05% |
| 2004 | 258000 | Kilograms | -6.86% |
| 2005 | 256000 | Kilograms | -0.78% |
| 2006 | 252000 | Kilograms | -1.56% |
| 2007 | 238000 | Kilograms | -5.56% |
| 2008 | 233000 | Kilograms | -2.10% |
| 2009 | 223000 | Kilograms | -4.29% |
| 2010 | 231000 | Kilograms | 3.59% |
| 2011 | 234000 | Kilograms | 1.30% |
| 2012 | 235000 | Kilograms | 0.43% |
