Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 10228 | Thousand metric tons | NA |
| 2004 | 10180 | Thousand metric tons | -0.47% |
| 2005 | 10236 | Thousand metric tons | 0.55% |
| 2006 | 10736 | Thousand metric tons | 4.88% |
| 2007 | 10960 | Thousand metric tons | 2.09% |
| 2008 | 10137 | Thousand metric tons | -7.51% |
| 2009 | 7674 | Thousand metric tons | -24.30% |
| 2010 | 7235 | Thousand metric tons | -5.72% |
| 2011 | 6600 | Thousand metric tons | -8.78% |
| 2012 | 7252 | Thousand metric tons | 9.88% |
