Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 306444 | Metric tons | NA |
| 2004 | 366174 | Metric tons | 19.49 % |
| 2005 | 386759 | Metric tons | 5.62 % |
| 2006 | 382718 | Metric tons | -1.04 % |
| 2007 | 399314 | Metric tons | 4.34 % |
| 2008 | 399320 | Metric tons | 0.00 % |
| 2009 | 400000 | Metric tons | 0.17 % |
