Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 688.106018066406 | Thousand metric tons | NA |
| 2003 | 625.002014160156 | Thousand metric tons | -9.17% |
| 2004 | 507.710998535156 | Thousand metric tons | -18.77% |
| 2005 | 607.559020996094 | Thousand metric tons | 19.67% |
| 2006 | 644.151000976563 | Thousand metric tons | 6.02% |
| 2007 | 623.929992675781 | Thousand metric tons | -3.14% |
| 2008 | 473.273010253906 | Thousand metric tons | -24.15% |
| 2009 | 280.772003173828 | Thousand metric tons | -40.67% |
| 2010 | 77.0479965209961 | Thousand metric tons | -72.56% |
| 2011 | 174.458999633789 | Thousand metric tons | 126.43% |
| 2012 | 173.25700378418 | Thousand metric tons | -0.69% |
