Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 11600 | Metric tons | NA |
| 2004 | 11500 | Metric tons | -0.86% |
| 2005 | 11700 | Metric tons | 1.74% |
| 2006 | 11700 | Metric tons | 0.00% |
| 2007 | 11400 | Metric tons | -2.56% |
| 2008 | 10000 | Metric tons | -12.28% |
| 2009 | 11000 | Metric tons | 10.00% |
| 2010 | 11000 | Metric tons | 0.00% |
| 2011 | 10000 | Metric tons | -9.09% |
| 2012 | 10000 | Metric tons | 0.00% |
