Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 400000 | Metric tons | NA |
| 2004 | 400000 | Metric tons | 0.00% |
| 2005 | 400000 | Metric tons | 0.00% |
| 2006 | 272000 | Metric tons | -32.00% |
| 2007 | 250000 | Metric tons | -8.09% |
| 2008 | 276000 | Metric tons | 10.40% |
| 2009 | 276000 | Metric tons | 0.00% |
