Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 80000 | Metric tons | NA |
| 2003 | 80000 | Metric tons | 0.00% |
| 2004 | 110000 | Metric tons | 37.50% |
| 2005 | 110000 | Metric tons | 0.00% |
| 2006 | 100000 | Metric tons | -9.09% |
| 2007 | 95000 | Metric tons | -5.00% |
| 2008 | 95000 | Metric tons | 0.00% |
| 2009 | 95000 | Metric tons | 0.00% |
| 2010 | 90000 | Metric tons | -5.26% |
| 2011 | 91500 | Metric tons | 1.67% |
| 2012 | 95600 | Metric tons | 4.48% |
