Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 17500 | Metric tons | NA |
| 2003 | 17500 | Metric tons | 0.00% |
| 2004 | 17500 | Metric tons | 0.00% |
| 2005 | 17500 | Metric tons | 0.00% |
| 2006 | 17500 | Metric tons | 0.00% |
| 2007 | 18000 | Metric tons | 2.86% |
| 2008 | 17000 | Metric tons | -5.56% |
| 2009 | 18000 | Metric tons | 5.88% |
| 2010 | 19000 | Metric tons | 5.56% |
| 2011 | 21000 | Metric tons | 10.53% |
| 2012 | 22000 | Metric tons | 4.76% |
| 2013 | 22000 | Metric tons | 0.00% |
