Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 38815 | Metric tons | NA |
| 2003 | 40202 | Metric tons | 3.57 % |
| 2004 | 67675 | Metric tons | 68.34 % |
| 2005 | 42145 | Metric tons | -37.72 % |
| 2006 | 38470 | Metric tons | -8.72 % |
| 2007 | 39019 | Metric tons | 1.43 % |
| 2008 | 39037 | Metric tons | 0.05 % |
| 2009 | 37503 | Metric tons | -3.93 % |
