Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2009 | 28.7830009460449 | Thousand metric tons | NA |
| 2010 | 30.8159999847412 | Thousand metric tons | 7.06% |
| 2011 | 23.1439990997314 | Thousand metric tons | -24.90% |
| 2012 | 16.5060005187988 | Thousand metric tons | -28.68% |
| 2013 | 16.5 | Thousand metric tons | -0.04% |
