Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2009 | 3800000 | Metric tons | NA |
| 2010 | 4600000 | Metric tons | 21.05% |
| 2011 | 4200000 | Metric tons | -8.70% |
| 2012 | 4400000 | Metric tons | 4.76% |
| 2013 | 4400000 | Metric tons | 0.00% |
