Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2009 | 6200 | Thousand metric tons | NA |
| 2010 | 5867 | Thousand metric tons | -5.37% |
| 2011 | 5430 | Thousand metric tons | -7.45% |
| 2012 | 5457 | Thousand metric tons | 0.50% |
| 2013 | 6100 | Thousand metric tons | 11.78% |
