Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 109.800003051758 | Thousand metric tons | NA |
| 2004 | 120.699996948242 | Thousand metric tons | 9.93% |
| 2005 | 138.5 | Thousand metric tons | 14.75% |
| 2006 | 118.099998474121 | Thousand metric tons | -14.73% |
| 2007 | 111.015998840332 | Thousand metric tons | -6.00% |
| 2008 | 83.3280029296875 | Thousand metric tons | -24.94% |
| 2009 | 35.1479988098145 | Thousand metric tons | -57.82% |
| 2010 | 40.1769981384277 | Thousand metric tons | 14.31% |
| 2011 | 40 | Thousand metric tons | -0.44% |
| 2012 | 40 | Thousand metric tons | 0.00% |
| 2013 | 40 | Thousand metric tons | 0.00% |
