Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2009 | 222.942001342773 | Thousand metric tons | NA |
| 2010 | 276.131011962891 | Thousand metric tons | 23.86% |
| 2011 | 364.221984863281 | Thousand metric tons | 31.90% |
| 2012 | 463.959991455078 | Thousand metric tons | 27.38% |
| 2013 | 470 | Thousand metric tons | 1.30% |
