Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 276 | Thousand metric tons | NA |
| 2004 | 269.139007568359 | Thousand metric tons | -2.49% |
| 2005 | 269.743011474609 | Thousand metric tons | 0.22% |
| 2006 | 303.795013427734 | Thousand metric tons | 12.62% |
| 2007 | 276.799987792969 | Thousand metric tons | -8.89% |
| 2008 | 312.669006347656 | Thousand metric tons | 12.96% |
| 2009 | 300 | Thousand metric tons | -4.05% |
| 2010 | 300 | Thousand metric tons | 0.00% |
| 2011 | 300 | Thousand metric tons | 0.00% |
| 2012 | 300 | Thousand metric tons | 0.00% |
| 2013 | 300 | Thousand metric tons | 0.00% |
