Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 342.700012207031 | Thousand metric tons | NA |
| 2004 | 359.600006103516 | Thousand metric tons | 4.93% |
| 2005 | 368.5 | Thousand metric tons | 2.47% |
| 2006 | 360.299987792969 | Thousand metric tons | -2.23% |
| 2007 | 364.600006103516 | Thousand metric tons | 1.19% |
| 2008 | 326 | Thousand metric tons | -10.59% |
| 2009 | 253 | Thousand metric tons | -22.39% |
| 2010 | 186 | Thousand metric tons | -26.48% |
| 2011 | 213 | Thousand metric tons | 14.52% |
| 2012 | 60 | Thousand metric tons | -71.83% |
| 2013 | 44 | Thousand metric tons | -26.67% |
