Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 29481 | Thousand metric tons | NA |
| 2004 | 30018 | Thousand metric tons | 1.82% |
| 2005 | 28854 | Thousand metric tons | -3.88% |
| 2006 | 30360 | Thousand metric tons | 5.22% |
| 2007 | 31149 | Thousand metric tons | 2.60% |
| 2008 | 29111 | Thousand metric tons | -6.54% |
| 2009 | 20104 | Thousand metric tons | -30.94% |
| 2010 | 28560 | Thousand metric tons | 42.06% |
| 2011 | 27943 | Thousand metric tons | -2.16% |
| 2012 | 27048 | Thousand metric tons | -3.20% |
