Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2009 | 3765.56396484375 | Thousand metric tons | NA |
| 2010 | 4044.25390625 | Thousand metric tons | 7.40% |
| 2011 | 6546.43115234375 | Thousand metric tons | 61.87% |
| 2012 | 5254.81298828125 | Thousand metric tons | -19.73% |
| 2013 | 5300 | Thousand metric tons | 0.86% |
