Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 339000 | Metric tons | NA |
| 2004 | 323000 | Metric tons | -4.72% |
| 2005 | 316000 | Metric tons | -2.17% |
| 2006 | 300000 | Metric tons | -5.06% |
| 2007 | 307253 | Metric tons | 2.42% |
