Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2004 | 51.4000015258789 | Thousand metric tons | NA |
| 2005 | 44.2000007629395 | Thousand metric tons | -14.01% |
| 2006 | 43.7000007629395 | Thousand metric tons | -1.13% |
| 2007 | 54.5999984741211 | Thousand metric tons | 24.94% |
| 2008 | 55 | Thousand metric tons | 0.73% |
| 2009 | 40.0999984741211 | Thousand metric tons | -27.09% |
| 2010 | 38.7000007629395 | Thousand metric tons | -3.49% |
| 2011 | 34 | Thousand metric tons | -12.14% |
| 2012 | 32 | Thousand metric tons | -5.88% |
| 2013 | 33 | Thousand metric tons | 3.13% |
