Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 478796 | Metric tons | NA |
| 2004 | 404549 | Metric tons | -15.51% |
| 2005 | 352374 | Metric tons | -12.90% |
| 2006 | 363998 | Metric tons | 3.30% |
| 2007 | 384709 | Metric tons | 5.69% |
| 2008 | 414336 | Metric tons | 7.70% |
| 2009 | 326461 | Metric tons | -21.21% |
| 2010 | 362623 | Metric tons | 11.08% |
| 2011 | 375332 | Metric tons | 3.50% |
| 2012 | 375000 | Metric tons | -0.09% |
| 2013 | 375000 | Metric tons | 0.00% |
