Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 112 | Thousand metric tons | NA |
| 2004 | 125 | Thousand metric tons | 11.61% |
| 2005 | 130.005004882813 | Thousand metric tons | 4.00% |
| 2006 | 130 | Thousand metric tons | 0.00% |
| 2007 | 120 | Thousand metric tons | -7.69% |
| 2008 | 115 | Thousand metric tons | -4.17% |
| 2009 | 110 | Thousand metric tons | -4.35% |
| 2010 | 110 | Thousand metric tons | 0.00% |
| 2011 | 100 | Thousand metric tons | -9.09% |
| 2012 | 100 | Thousand metric tons | 0.00% |
