Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 6.46299982070923 | Thousand metric tons | NA |
| 2004 | 6.43300008773804 | Thousand metric tons | -0.46% |
| 2005 | 6.5 | Thousand metric tons | 1.04% |
| 2006 | 6.59999990463257 | Thousand metric tons | 1.54% |
| 2007 | 6.59999990463257 | Thousand metric tons | 0.00% |
| 2008 | 6.59999990463257 | Thousand metric tons | 0.00% |
| 2009 | 39 | Thousand metric tons | 490.91% |
| 2010 | 54 | Thousand metric tons | 38.46% |
| 2011 | 47 | Thousand metric tons | -12.96% |
| 2012 | 31 | Thousand metric tons | -34.04% |
| 2013 | 33 | Thousand metric tons | 6.45% |
