Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2009 | 265.700012207031 | Thousand metric tons | NA |
| 2010 | 271.799987792969 | Thousand metric tons | 2.30% |
| 2011 | 280.799987792969 | Thousand metric tons | 3.31% |
| 2012 | 275 | Thousand metric tons | -2.07% |
| 2013 | 275 | Thousand metric tons | 0.00% |
