Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 600 | Thousand metric tons | NA |
| 2003 | 768 | Thousand metric tons | 28.00% |
| 2004 | 751.539978027344 | Thousand metric tons | -2.14% |
| 2005 | 827.370971679688 | Thousand metric tons | 10.09% |
| 2006 | 867.348999023438 | Thousand metric tons | 4.83% |
| 2007 | 902.130981445313 | Thousand metric tons | 4.01% |
| 2008 | 916 | Thousand metric tons | 1.54% |
| 2009 | 909 | Thousand metric tons | -0.76% |
| 2010 | 820 | Thousand metric tons | -9.79% |
| 2011 | 981 | Thousand metric tons | 19.63% |
| 2012 | 683 | Thousand metric tons | -30.38% |
