Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 2870 | Metric tons | NA |
| 2003 | 2921 | Metric tons | 1.78 % |
| 2004 | 3060 | Metric tons | 4.76 % |
| 2005 | 3206 | Metric tons | 4.77 % |
| 2006 | 3470.66088867188 | Metric tons | 8.26 % |
| 2007 | 3493.90893554688 | Metric tons | 0.67 % |
| 2008 | 3685.93090820313 | Metric tons | 5.50 % |
| 2009 | 3854.00390625 | Metric tons | 4.56 % |
