Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 10604 | Thousand metric tons | NA |
| 2004 | 10664 | Thousand metric tons | 0.57% |
| 2005 | 11423 | Thousand metric tons | 7.12% |
| 2006 | 11497 | Thousand metric tons | 0.65% |
| 2007 | 11110 | Thousand metric tons | -3.37% |
| 2008 | 10373 | Thousand metric tons | -6.63% |
| 2009 | 5719 | Thousand metric tons | -44.87% |
| 2010 | 8549 | Thousand metric tons | 49.48% |
| 2011 | 9800 | Thousand metric tons | 14.63% |
| 2012 | 9418 | Thousand metric tons | -3.90% |
