Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2009 | 8382.21484375 | Thousand metric tons | NA |
| 2010 | 7694.87890625 | Thousand metric tons | -8.20% |
| 2011 | 9966.0380859375 | Thousand metric tons | 29.52% |
| 2012 | 8057.1298828125 | Thousand metric tons | -19.15% |
| 2013 | 6576.9599609375 | Thousand metric tons | -18.37% |
