Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 165 | Thousand metric tons | NA |
| 2004 | 166.600006103516 | Thousand metric tons | 0.97% |
| 2005 | 165 | Thousand metric tons | -0.96% |
| 2006 | 163.300003051758 | Thousand metric tons | -1.03% |
| 2007 | 166 | Thousand metric tons | 1.65% |
| 2008 | 160 | Thousand metric tons | -3.61% |
| 2009 | 130.40299987793 | Thousand metric tons | -18.50% |
| 2010 | 130 | Thousand metric tons | -0.31% |
| 2011 | 132 | Thousand metric tons | 1.54% |
| 2012 | 135 | Thousand metric tons | 2.27% |
| 2013 | 133 | Thousand metric tons | -1.48% |
