Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 7000 | Thousand metric tons | NA |
| 2003 | 7700 | Thousand metric tons | 10.00% |
| 2004 | 5000 | Thousand metric tons | -35.06% |
| 2005 | 5800 | Thousand metric tons | 16.00% |
| 2006 | 7200 | Thousand metric tons | 24.14% |
| 2007 | 9000 | Thousand metric tons | 25.00% |
| 2008 | 8044 | Thousand metric tons | -10.62% |
| 2009 | 7900 | Thousand metric tons | -1.79% |
| 2010 | 7120 | Thousand metric tons | -9.87% |
| 2011 | 7760 | Thousand metric tons | 8.99% |
| 2012 | 7700 | Thousand metric tons | -0.77% |
