Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 512.1669921875 | Thousand metric tons | NA |
| 2004 | 821.031005859375 | Thousand metric tons | 60.31% |
| 2005 | 632.7919921875 | Thousand metric tons | -22.93% |
| 2006 | 533.534973144531 | Thousand metric tons | -15.69% |
| 2007 | 669.578002929688 | Thousand metric tons | 25.50% |
| 2008 | 785.552978515625 | Thousand metric tons | 17.32% |
| 2009 | 505.983001708984 | Thousand metric tons | -35.59% |
| 2010 | 622.968017578125 | Thousand metric tons | 23.12% |
| 2011 | 648.806030273438 | Thousand metric tons | 4.15% |
| 2012 | 479.411987304688 | Thousand metric tons | -26.11% |
| 2013 | 500 | Thousand metric tons | 4.29% |
