Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 77.1999969482422 | Thousand metric tons | NA |
| 2004 | 85.9000015258789 | Thousand metric tons | 11.27% |
| 2005 | 90.4000015258789 | Thousand metric tons | 5.24% |
| 2006 | 88 | Thousand metric tons | -2.65% |
| 2007 | 87 | Thousand metric tons | -1.14% |
| 2008 | 91 | Thousand metric tons | 4.60% |
| 2009 | 73 | Thousand metric tons | -19.78% |
| 2010 | 76 | Thousand metric tons | 4.11% |
| 2011 | 69 | Thousand metric tons | -9.21% |
| 2012 | 69 | Thousand metric tons | 0.00% |
| 2013 | 75 | Thousand metric tons | 8.70% |
