Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 32036 | Thousand metric tons | NA |
| 2004 | 34579 | Thousand metric tons | 7.94% |
| 2005 | 33884 | Thousand metric tons | -2.01% |
| 2006 | 32452 | Thousand metric tons | -4.23% |
| 2007 | 35571 | Thousand metric tons | 9.61% |
| 2008 | 34871 | Thousand metric tons | -1.97% |
| 2009 | 25135 | Thousand metric tons | -27.92% |
| 2010 | 25000 | Thousand metric tons | -0.54% |
| 2011 | 31000 | Thousand metric tons | 24.00% |
| 2012 | 27000 | Thousand metric tons | -12.90% |
