Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 50 | Thousand metric tons | NA |
| 2004 | 58 | Thousand metric tons | 16.00% |
| 2005 | 47 | Thousand metric tons | -18.97% |
| 2006 | 43 | Thousand metric tons | -8.51% |
| 2007 | 45 | Thousand metric tons | 4.65% |
| 2008 | 38.2999992370605 | Thousand metric tons | -14.89% |
| 2009 | 41.2000007629395 | Thousand metric tons | 7.57% |
| 2010 | 67.3000030517578 | Thousand metric tons | 63.35% |
| 2011 | 53.4000015258789 | Thousand metric tons | -20.65% |
| 2012 | 53.9090003967285 | Thousand metric tons | 0.95% |
| 2013 | 57.0069999694824 | Thousand metric tons | 5.75% |
