Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 6326 | Thousand metric tons | NA |
| 2003 | 7291 | Thousand metric tons | 15.25% |
| 2004 | 7169.205078125 | Thousand metric tons | -1.67% |
| 2005 | 7113.0732421875 | Thousand metric tons | -0.78% |
| 2006 | 8354.9013671875 | Thousand metric tons | 17.46% |
| 2007 | 8569.400390625 | Thousand metric tons | 2.57% |
| 2008 | 8000 | Thousand metric tons | -6.64% |
| 2009 | 8679 | Thousand metric tons | 8.49% |
| 2010 | 9985 | Thousand metric tons | 15.05% |
| 2011 | 8954.625 | Thousand metric tons | -10.32% |
| 2012 | 6259 | Thousand metric tons | -30.10% |
| 2013 | 6300 | Thousand metric tons | 0.66% |
