Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 525000 | Metric tons | NA |
| 2004 | 525000 | Metric tons | 0.00 % |
| 2005 | 525000 | Metric tons | 0.00 % |
| 2006 | 525000 | Metric tons | 0.00 % |
| 2007 | 525000 | Metric tons | 0.00 % |
| 2008 | 525000 | Metric tons | 0.00 % |
| 2009 | 862935 | Metric tons | 64.37 % |
| 2010 | 760000 | Metric tons | -11.93 % |
| 2011 | 842870 | Metric tons | 10.90 % |
| 2012 | 680000 | Metric tons | -19.32 % |
| 2013 | 600000 | Metric tons | -11.76 % |
