Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1010000 | Metric tons | NA |
| 2004 | 900000 | Metric tons | -10.89% |
| 2005 | 800000 | Metric tons | -11.11% |
| 2006 | 800000 | Metric tons | 0.00% |
| 2007 | 750000 | Metric tons | -6.25% |
| 2008 | 700000 | Metric tons | -6.67% |
