Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 1200000 | Metric tons | NA |
| 2004 | 1200000 | Metric tons | 0.00% |
| 2005 | 1100000 | Metric tons | -8.33% |
| 2006 | 1200000 | Metric tons | 9.09% |
| 2007 | 1200000 | Metric tons | 0.00% |
| 2008 | 1200000 | Metric tons | 0.00% |
| 2009 | 1000000 | Metric tons | -16.67% |
