Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 11600 | Metric tons | NA |
| 2004 | 11500 | Metric tons | -0.86 % |
| 2005 | 11700 | Metric tons | 1.74 % |
| 2006 | 11700 | Metric tons | 0.00 % |
| 2007 | 11400 | Metric tons | -2.56 % |
