Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2009 | 3831 | Thousand metric tons | NA |
| 2010 | 4096.7001953125 | Thousand metric tons | 6.94% |
| 2011 | 4281.7998046875 | Thousand metric tons | 4.52% |
| 2012 | 3926 | Thousand metric tons | -8.31% |
| 2013 | 4430 | Thousand metric tons | 12.84% |
