Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2009 | 6166 | Thousand metric tons | NA |
| 2010 | 6666 | Thousand metric tons | 8.11% |
| 2011 | 6700 | Thousand metric tons | 0.51% |
| 2012 | 6700 | Thousand metric tons | 0.00% |
| 2013 | 6700 | Thousand metric tons | 0.00% |
