Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2009 | 133.358001708984 | Thousand metric tons | NA |
| 2010 | 97.1360015869141 | Thousand metric tons | -27.16% |
| 2011 | 100 | Thousand metric tons | 2.95% |
| 2012 | 100 | Thousand metric tons | 0.00% |
| 2013 | 100 | Thousand metric tons | 0.00% |
