Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 132 | Thousand metric tons | NA |
| 2004 | 132 | Thousand metric tons | 0.00% |
| 2005 | 132 | Thousand metric tons | 0.00% |
| 2006 | 135 | Thousand metric tons | 2.27% |
| 2007 | 135 | Thousand metric tons | 0.00% |
| 2008 | 138 | Thousand metric tons | 2.22% |
| 2009 | 32.1049995422363 | Thousand metric tons | -76.74% |
| 2010 | 36 | Thousand metric tons | 12.13% |
| 2011 | 37 | Thousand metric tons | 2.78% |
| 2012 | 38 | Thousand metric tons | 2.70% |
| 2013 | 35 | Thousand metric tons | -7.89% |
