Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 2402.19995117188 | Thousand metric tons | NA |
| 2004 | 2392.19995117188 | Thousand metric tons | -0.42% |
| 2005 | 2645.60009765625 | Thousand metric tons | 10.59% |
| 2006 | 2481 | Thousand metric tons | -6.22% |
| 2007 | 2593 | Thousand metric tons | 4.51% |
| 2008 | 2581 | Thousand metric tons | -0.46% |
| 2009 | 2042 | Thousand metric tons | -20.88% |
| 2010 | 2532 | Thousand metric tons | 24.00% |
| 2011 | 2795 | Thousand metric tons | 10.39% |
| 2012 | 2078 | Thousand metric tons | -25.65% |
