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 | 3922.7080078125 | Metric tons | 6.42% |
| 2010 | 3640.46508789063 | Metric tons | -7.20% |
| 2011 | 3418.86206054688 | Metric tons | -6.09% |
| 2012 | 3479.05810546875 | Metric tons | 1.76% |
