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 | 6.5 | Thousand metric tons | -1.52 % |
