Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2005 | 413340 | Metric tons | NA |
| 2006 | 389471 | Metric tons | -5.77 % |
| 2007 | 401204 | Metric tons | 3.01 % |
| 2008 | 401210 | Metric tons | 0.00 % |
| 2009 | 401300 | Metric tons | 0.02 % |
