Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 5000 | Thousand metric tons | NA |
| 2003 | 5000 | Thousand metric tons | 0.00% |
| 2004 | 5000 | Thousand metric tons | 0.00% |
| 2005 | 5100 | Thousand metric tons | 2.00% |
| 2006 | 5100 | Thousand metric tons | 0.00% |
| 2007 | 5100 | Thousand metric tons | 0.00% |
| 2008 | 10000 | Thousand metric tons | 96.08% |
| 2009 | 12000 | Thousand metric tons | 20.00% |
| 2010 | 13770 | Thousand metric tons | 14.75% |
| 2011 | 14690 | Thousand metric tons | 6.68% |
| 2012 | 15000 | Thousand metric tons | 2.11% |
