Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2004 | 337 | Thousand metric tons | NA |
| 2005 | 381 | Thousand metric tons | 13.06% |
| 2006 | 376 | Thousand metric tons | -1.31% |
| 2007 | 742 | Thousand metric tons | 97.34% |
| 2008 | 740 | Thousand metric tons | -0.27% |
| 2009 | 711 | Thousand metric tons | -3.92% |
| 2010 | 679 | Thousand metric tons | -4.50% |
| 2011 | 676 | Thousand metric tons | -0.44% |
| 2012 | 436.200012207031 | Thousand metric tons | -35.47% |
| 2013 | 450 | Thousand metric tons | 3.16% |
