Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2004 | 139.520004272461 | Thousand metric tons | NA |
| 2005 | 152.938995361328 | Thousand metric tons | 9.62% |
| 2006 | 131.936004638672 | Thousand metric tons | -13.73% |
| 2007 | 154.294006347656 | Thousand metric tons | 16.95% |
| 2008 | 154 | Thousand metric tons | -0.19% |
| 2009 | 74.302001953125 | Thousand metric tons | -51.75% |
| 2010 | 64.5699996948242 | Thousand metric tons | -13.10% |
| 2011 | 71.870002746582 | Thousand metric tons | 11.31% |
| 2012 | 73.6650009155273 | Thousand metric tons | 2.50% |
| 2013 | 74 | Thousand metric tons | 0.45% |
