Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 150000 | Metric tons | NA |
| 2004 | 152077 | Metric tons | 1.38 % |
| 2005 | 160000 | Metric tons | 5.21 % |
| 2006 | 160000 | Metric tons | 0.00 % |
| 2007 | 160000 | Metric tons | 0.00 % |
