Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 12756 | Thousand metric tons | NA |
| 2004 | 13198 | Thousand metric tons | 3.47% |
| 2005 | 12705 | Thousand metric tons | -3.74% |
| 2006 | 13013 | Thousand metric tons | 2.42% |
| 2007 | 12426 | Thousand metric tons | -4.51% |
| 2008 | 11372 | Thousand metric tons | -8.48% |
| 2009 | 8105 | Thousand metric tons | -28.73% |
| 2010 | 10137 | Thousand metric tons | 25.07% |
| 2011 | 9700 | Thousand metric tons | -4.31% |
| 2012 | 9531 | Thousand metric tons | -1.74% |
