Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 3669 | Metric tons | NA |
| 2003 | 3609 | Metric tons | -1.64% |
| 2004 | 3544 | Metric tons | -1.80% |
| 2005 | 4542 | Metric tons | 28.16% |
| 2006 | 5152 | Metric tons | 13.43% |
| 2007 | 6118 | Metric tons | 18.75% |
| 2008 | 5593 | Metric tons | -8.58% |
| 2009 | 4323 | Metric tons | -22.71% |
| 2010 | 4515 | Metric tons | 4.44% |
| 2011 | 4245 | Metric tons | -5.98% |
| 2012 | 3967 | Metric tons | -6.55% |
| 2013 | 4000 | Metric tons | 0.83% |
