Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1384 | Thousand metric tons | NA |
| 2004 | 1464 | Thousand metric tons | 5.78% |
| 2005 | 1737 | Thousand metric tons | 18.65% |
| 2006 | 1592 | Thousand metric tons | -8.35% |
| 2007 | 1438 | Thousand metric tons | -9.67% |
| 2008 | 1679 | Thousand metric tons | 16.76% |
| 2009 | 1584 | Thousand metric tons | -5.66% |
| 2010 | 1454 | Thousand metric tons | -8.21% |
| 2011 | 1500 | Thousand metric tons | 3.16% |
| 2012 | 1500 | Thousand metric tons | 0.00% |
| 2013 | 1500 | Thousand metric tons | 0.00% |
