Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 2200 | Metric tons | NA |
| 2003 | 2400 | Metric tons | 9.09% |
| 2004 | 2450 | Metric tons | 2.08% |
| 2005 | 2500 | Metric tons | 2.04% |
| 2006 | 2600 | Metric tons | 4.00% |
| 2007 | 2700 | Metric tons | 3.85% |
| 2008 | 2800 | Metric tons | 3.70% |
| 2009 | 2900 | Metric tons | 3.57% |
| 2010 | 3500 | Metric tons | 20.69% |
| 2011 | 3700 | Metric tons | 5.71% |
| 2012 | 3900 | Metric tons | 5.41% |
