Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2009 | 328.153015136719 | Thousand metric tons | NA |
| 2010 | 305.881988525391 | Thousand metric tons | -6.79% |
| 2011 | 173.35400390625 | Thousand metric tons | -43.33% |
| 2012 | 58.1570014953613 | Thousand metric tons | -66.45% |
| 2013 | 61.7179985046387 | Thousand metric tons | 6.12% |
