Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1250 | Thousand metric tons | NA |
| 2004 | 1264 | Thousand metric tons | 1.12% |
| 2005 | 1211 | Thousand metric tons | -4.19% |
| 2006 | 1218 | Thousand metric tons | 0.58% |
| 2007 | 1277 | Thousand metric tons | 4.84% |
| 2008 | 1200 | Thousand metric tons | -6.03% |
| 2009 | 1000 | Thousand metric tons | -16.67% |
| 2010 | 1000 | Thousand metric tons | 0.00% |
| 2011 | 1000 | Thousand metric tons | 0.00% |
| 2012 | 1000 | Thousand metric tons | 0.00% |
| 2013 | 1000 | Thousand metric tons | 0.00% |
