Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 425942 | Metric tons | NA |
| 2004 | 326928 | Metric tons | -23.25 % |
| 2005 | 494511 | Metric tons | 51.26 % |
| 2006 | 341223 | Metric tons | -31.00 % |
| 2007 | 350000 | Metric tons | 2.57 % |
