Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 45.3709983825684 | Thousand metric tons | NA |
| 2004 | 45.806999206543 | Thousand metric tons | 0.96 % |
| 2005 | 54.507999420166 | Thousand metric tons | 18.99 % |
| 2006 | 57.6199989318848 | Thousand metric tons | 5.71 % |
| 2007 | 58.7360000610352 | Thousand metric tons | 1.94 % |
| 2008 | 47.5429992675781 | Thousand metric tons | -19.06 % |
| 2009 | 47 | Thousand metric tons | -1.14 % |
