Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 937 | Thousand metric tons | NA |
| 2003 | 949 | Thousand metric tons | 1.28% |
| 2004 | 1032.43005371094 | Thousand metric tons | 8.79% |
| 2005 | 1000 | Thousand metric tons | -3.14% |
| 2006 | 1000 | Thousand metric tons | 0.00% |
| 2007 | 1000 | Thousand metric tons | 0.00% |
| 2008 | 1000 | Thousand metric tons | 0.00% |
| 2009 | 1000 | Thousand metric tons | 0.00% |
| 2010 | 890 | Thousand metric tons | -11.00% |
| 2011 | 730 | Thousand metric tons | -17.98% |
| 2012 | 900 | Thousand metric tons | 23.29% |
