Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 21600 | Metric tons | NA |
| 2003 | 27400 | Metric tons | 26.85% |
| 2004 | 22500 | Metric tons | -17.88% |
| 2005 | 26100 | Metric tons | 16.00% |
| 2006 | 24000 | Metric tons | -8.05% |
| 2007 | 24000 | Metric tons | 0.00% |
| 2008 | 28800 | Metric tons | 20.00% |
| 2009 | 28595 | Metric tons | -0.71% |
| 2010 | 20833 | Metric tons | -27.14% |
| 2011 | 31929 | Metric tons | 53.26% |
| 2012 | 35708 | Metric tons | 11.84% |
