Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 168 | Thousand metric tons | NA |
| 2004 | 176 | Thousand metric tons | 4.76% |
| 2005 | 188 | Thousand metric tons | 6.82% |
| 2006 | 216 | Thousand metric tons | 14.89% |
| 2007 | 234 | Thousand metric tons | 8.33% |
| 2008 | 234 | Thousand metric tons | 0.00% |
| 2009 | 128 | Thousand metric tons | -45.30% |
| 2010 | 110 | Thousand metric tons | -14.06% |
| 2011 | 115 | Thousand metric tons | 4.55% |
| 2012 | 114 | Thousand metric tons | -0.87% |
| 2013 | 114 | Thousand metric tons | 0.00% |
