Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 21000 | Metric tons | NA |
| 2004 | 22925 | Metric tons | 9.17% |
| 2005 | 27076 | Metric tons | 18.11% |
| 2006 | 32824 | Metric tons | 21.23% |
| 2007 | 32814 | Metric tons | -0.03% |
| 2008 | 32000 | Metric tons | -2.48% |
