Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 662 | Thousand metric tons | NA |
| 2003 | 661 | Thousand metric tons | -0.15% |
| 2004 | 630.443969726563 | Thousand metric tons | -4.62% |
| 2005 | 660.752990722656 | Thousand metric tons | 4.81% |
| 2006 | 845.330993652344 | Thousand metric tons | 27.93% |
| 2007 | 773.119018554688 | Thousand metric tons | -8.54% |
| 2008 | 773.794006347656 | Thousand metric tons | 0.09% |
| 2009 | 723.927978515625 | Thousand metric tons | -6.44% |
| 2010 | 758.010986328125 | Thousand metric tons | 4.71% |
| 2011 | 917.758972167969 | Thousand metric tons | 21.07% |
| 2012 | 799.064025878906 | Thousand metric tons | -12.93% |
| 2013 | 1015.15802001953 | Thousand metric tons | 27.04% |
