Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 50 | Thousand metric tons | NA |
| 2004 | 57.2290000915527 | Thousand metric tons | 14.46% |
| 2005 | 60 | Thousand metric tons | 4.84% |
| 2006 | 60 | Thousand metric tons | 0.00% |
| 2007 | 60 | Thousand metric tons | 0.00% |
| 2008 | 60 | Thousand metric tons | 0.00% |
| 2009 | 58.6780014038086 | Thousand metric tons | -2.20% |
| 2010 | 64.9619979858398 | Thousand metric tons | 10.71% |
| 2011 | 65 | Thousand metric tons | 0.06% |
| 2012 | 65 | Thousand metric tons | 0.00% |
| 2013 | 65 | Thousand metric tons | 0.00% |
