Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 7 | Thousand metric tons | NA |
| 2004 | 7 | Thousand metric tons | 0.00% |
| 2005 | 7.67000007629395 | Thousand metric tons | 9.57% |
| 2006 | 8.9680004119873 | Thousand metric tons | 16.92% |
| 2007 | 5.55499982833862 | Thousand metric tons | -38.06% |
| 2008 | 4.42999982833862 | Thousand metric tons | -20.25% |
| 2009 | 4.34999990463257 | Thousand metric tons | -1.81% |
| 2010 | 4.08199977874756 | Thousand metric tons | -6.16% |
| 2011 | 4.22399997711182 | Thousand metric tons | 3.48% |
| 2012 | 4.25 | Thousand metric tons | 0.62% |
