Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1800 | Thousand metric tons | NA |
| 2004 | 1800 | Thousand metric tons | 0.00% |
| 2005 | 1818 | Thousand metric tons | 1.00% |
| 2006 | 2000 | Thousand metric tons | 10.01% |
| 2007 | 2000 | Thousand metric tons | 0.00% |
| 2008 | 2000 | Thousand metric tons | 0.00% |
| 2009 | 1800 | Thousand metric tons | -10.00% |
| 2010 | 1900 | Thousand metric tons | 5.56% |
| 2011 | 1900 | Thousand metric tons | 0.00% |
| 2012 | 1800 | Thousand metric tons | -5.26% |
| 2013 | 1900 | Thousand metric tons | 5.56% |
