Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 111 | Thousand metric tons | NA |
| 2003 | 120 | Thousand metric tons | 8.11% |
| 2004 | 120 | Thousand metric tons | 0.00% |
| 2005 | 143 | Thousand metric tons | 19.17% |
| 2006 | 143 | Thousand metric tons | 0.00% |
| 2007 | 145 | Thousand metric tons | 1.40% |
| 2008 | 143 | Thousand metric tons | -1.38% |
| 2009 | 110 | Thousand metric tons | -23.08% |
| 2010 | 130 | Thousand metric tons | 18.18% |
| 2011 | 120 | Thousand metric tons | -7.69% |
| 2012 | 120 | Thousand metric tons | 0.00% |
