Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 563580 | Metric tons | NA |
| 2004 | 552507 | Metric tons | -1.96 % |
| 2005 | 580000 | Metric tons | 4.98 % |
| 2006 | 674766 | Metric tons | 16.34 % |
| 2007 | 675000 | Metric tons | 0.03 % |
| 2008 | 675000 | Metric tons | 0.00 % |
