Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 5845 | Thousand metric tons | NA |
| 2004 | 5846 | Thousand metric tons | 0.02% |
| 2005 | 6031 | Thousand metric tons | 3.16% |
| 2006 | 5417 | Thousand metric tons | -10.18% |
| 2007 | 6412 | Thousand metric tons | 18.37% |
| 2008 | 6130 | Thousand metric tons | -4.40% |
| 2009 | 4655 | Thousand metric tons | -24.06% |
| 2010 | 5799 | Thousand metric tons | 24.58% |
| 2011 | 5900 | Thousand metric tons | 1.74% |
| 2012 | 5909 | Thousand metric tons | 0.15% |
