Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 191.016998291016 | Thousand metric tons | NA |
| 2004 | 183 | Thousand metric tons | -4.20% |
| 2005 | 197 | Thousand metric tons | 7.65% |
| 2006 | 259.596008300781 | Thousand metric tons | 31.77% |
| 2007 | 183.188995361328 | Thousand metric tons | -29.43% |
| 2008 | 201.602996826172 | Thousand metric tons | 10.05% |
| 2009 | 109 | Thousand metric tons | -45.93% |
| 2010 | 107 | Thousand metric tons | -1.83% |
| 2011 | 238 | Thousand metric tons | 122.43% |
| 2012 | 190 | Thousand metric tons | -20.17% |
| 2013 | 300 | Thousand metric tons | 57.89% |
