Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 289000 | Metric tons | NA |
| 2004 | 336900 | Metric tons | 16.57 % |
| 2005 | 457400 | Metric tons | 35.77 % |
| 2006 | 431300 | Metric tons | -5.71 % |
| 2007 | 440000 | Metric tons | 2.02 % |
| 2008 | 440000 | Metric tons | 0.00 % |
