Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2009 | 18938.990234375 | Thousand metric tons | NA |
| 2010 | 19676.1640625 | Thousand metric tons | 3.89% |
| 2011 | 17442.748046875 | Thousand metric tons | -11.35% |
| 2012 | 14446 | Thousand metric tons | -17.18% |
| 2013 | 11900 | Thousand metric tons | -17.62% |
