Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 8.7819995880127 | Thousand metric tons | NA |
| 2004 | 9.10999965667725 | Thousand metric tons | 3.73 % |
| 2005 | 11.4519996643066 | Thousand metric tons | 25.71 % |
| 2006 | 15.1190004348755 | Thousand metric tons | 32.02 % |
| 2007 | 13.664999961853 | Thousand metric tons | -9.62 % |
| 2008 | 9.94799995422363 | Thousand metric tons | -27.20 % |
| 2009 | 10 | Thousand metric tons | 0.52 % |
