Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 51600 | Thousand metric tons | NA |
| 2003 | 48600 | Thousand metric tons | -5.81% |
| 2004 | 54700 | Thousand metric tons | 12.55% |
| 2005 | 54329.2421875 | Thousand metric tons | -0.68% |
| 2006 | 52749 | Thousand metric tons | -2.91% |
| 2007 | 52489 | Thousand metric tons | -0.49% |
| 2008 | 53600 | Thousand metric tons | 2.12% |
| 2009 | 26700 | Thousand metric tons | -50.19% |
| 2010 | 49900 | Thousand metric tons | 86.89% |
| 2011 | 54700 | Thousand metric tons | 9.62% |
| 2012 | 54000 | Thousand metric tons | -1.28% |
