Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 1224 | Thousand metric tons | NA |
| 2003 | 1268 | Thousand metric tons | 3.59% |
| 2004 | 1392 | Thousand metric tons | 9.78% |
| 2005 | 1384 | Thousand metric tons | -0.57% |
| 2006 | 1800 | Thousand metric tons | 30.06% |
| 2007 | 1800 | Thousand metric tons | 0.00% |
| 2008 | 1784 | Thousand metric tons | -0.89% |
| 2009 | 1800 | Thousand metric tons | 0.90% |
| 2010 | 1800 | Thousand metric tons | 0.00% |
| 2011 | 1710 | Thousand metric tons | -5.00% |
| 2012 | 1700 | Thousand metric tons | -0.58% |
