Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 2642 | Thousand metric tons | NA |
| 2003 | 2476 | Thousand metric tons | -6.28% |
| 2004 | 2588 | Thousand metric tons | 4.52% |
| 2005 | 2709 | Thousand metric tons | 4.68% |
| 2006 | 2952 | Thousand metric tons | 8.97% |
| 2007 | 2950 | Thousand metric tons | -0.07% |
| 2008 | 2934 | Thousand metric tons | -0.54% |
| 2009 | 1586 | Thousand metric tons | -45.94% |
| 2010 | 1796 | Thousand metric tons | 13.24% |
| 2011 | 2064 | Thousand metric tons | 14.92% |
| 2012 | 2500 | Thousand metric tons | 21.12% |
