Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 149000 | Metric tons | NA |
| 2004 | 176000 | Metric tons | 18.12% |
| 2005 | 202000 | Metric tons | 14.77% |
| 2006 | 200000 | Metric tons | -0.99% |
| 2007 | 200000 | Metric tons | 0.00% |
| 2008 | 200000 | Metric tons | 0.00% |
