Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 2727 | Metric tons | NA |
| 2003 | 2569 | Metric tons | -5.79% |
| 2004 | 2569 | Metric tons | 0.00% |
| 2005 | 2894.16088867188 | Metric tons | 12.66% |
| 2006 | 2969.84497070313 | Metric tons | 2.62% |
| 2007 | 3135.42993164063 | Metric tons | 5.58% |
| 2008 | 3236.31201171875 | Metric tons | 3.22% |
| 2009 | 3553.84106445313 | Metric tons | 9.81% |
| 2010 | 4410.7490234375 | Metric tons | 24.11% |
| 2011 | 4777.7099609375 | Metric tons | 8.32% |
| 2012 | 5358.19482421875 | Metric tons | 12.15% |
