Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 1000 | Thousand metric tons | NA |
| 2003 | 1000 | Thousand metric tons | 0.00% |
| 2004 | 920.809020996094 | Thousand metric tons | -7.92% |
| 2005 | 911.161987304688 | Thousand metric tons | -1.05% |
| 2006 | 936.072021484375 | Thousand metric tons | 2.73% |
| 2007 | 1006.416015625 | Thousand metric tons | 7.51% |
| 2008 | 1000 | Thousand metric tons | -0.64% |
| 2009 | 910.945007324219 | Thousand metric tons | -8.91% |
| 2010 | 872.273010253906 | Thousand metric tons | -4.25% |
| 2011 | 815.43798828125 | Thousand metric tons | -6.52% |
| 2012 | 791.960998535156 | Thousand metric tons | -2.88% |
| 2013 | 800 | Thousand metric tons | 1.02% |
