Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2009 | 189 | Thousand metric tons | NA |
| 2010 | 190 | Thousand metric tons | 0.53% |
| 2011 | 174.5 | Thousand metric tons | -8.16% |
| 2012 | 191.970001220703 | Thousand metric tons | 10.01% |
| 2013 | 190 | Thousand metric tons | -1.03% |
