Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 500000 | Metric tons | NA |
| 2004 | 400000 | Metric tons | -20.00% |
| 2005 | 400000 | Metric tons | 0.00% |
| 2006 | 360000 | Metric tons | -10.00% |
| 2007 | 390000 | Metric tons | 8.33% |
| 2008 | 380000 | Metric tons | -2.56% |
| 2009 | 440000 | Metric tons | 15.79% |
| 2010 | 400000 | Metric tons | -9.09% |
| 2011 | 440000 | Metric tons | 10.00% |
| 2012 | 420000 | Metric tons | -4.55% |
| 2013 | 420000 | Metric tons | 0.00% |
