Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 366.899993896484 | Thousand metric tons | NA |
| 2004 | 367.899993896484 | Thousand metric tons | 0.27% |
| 2005 | 604 | Thousand metric tons | 64.18% |
| 2006 | 521 | Thousand metric tons | -13.74% |
| 2007 | 322.5 | Thousand metric tons | -38.10% |
| 2008 | 321.5 | Thousand metric tons | -0.31% |
| 2009 | 558 | Thousand metric tons | 73.56% |
| 2010 | 342 | Thousand metric tons | -38.71% |
| 2011 | 400 | Thousand metric tons | 16.96% |
| 2012 | 386 | Thousand metric tons | -3.50% |
| 2013 | 386 | Thousand metric tons | 0.00% |
