Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 109 | Thousand metric tons | NA |
| 2003 | 161 | Thousand metric tons | 47.71% |
| 2004 | 119.5 | Thousand metric tons | -25.78% |
| 2005 | 166 | Thousand metric tons | 38.91% |
| 2006 | 187.600006103516 | Thousand metric tons | 13.01% |
| 2007 | 185.300003051758 | Thousand metric tons | -1.23% |
| 2008 | 237 | Thousand metric tons | 27.90% |
| 2009 | 232 | Thousand metric tons | -2.11% |
| 2010 | 188 | Thousand metric tons | -18.97% |
| 2011 | 203 | Thousand metric tons | 7.98% |
| 2012 | 180 | Thousand metric tons | -11.33% |
