Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 603498 | Metric tons | NA |
| 2003 | 557082 | Metric tons | -7.69 % |
| 2004 | 562795 | Metric tons | 1.03 % |
| 2005 | 595383 | Metric tons | 5.79 % |
| 2006 | 603295 | Metric tons | 1.33 % |
| 2007 | 596249 | Metric tons | -1.17 % |
| 2008 | 606999 | Metric tons | 1.80 % |
