Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2009 | 671000 | Metric tons | NA |
| 2010 | 561000 | Metric tons | -16.39% |
| 2011 | 739000 | Metric tons | 31.73% |
| 2012 | 996000 | Metric tons | 34.78% |
| 2013 | 1081000 | Metric tons | 8.53% |
