Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 21121 | Thousand metric tons | NA |
| 2003 | 24127 | Thousand metric tons | 14.23% |
| 2004 | 26153 | Thousand metric tons | 8.40% |
| 2005 | 30808 | Thousand metric tons | 17.80% |
| 2006 | 32690 | Thousand metric tons | 6.11% |
| 2007 | 36400 | Thousand metric tons | 11.35% |
| 2008 | 40009 | Thousand metric tons | 9.91% |
| 2009 | 48810 | Thousand metric tons | 22.00% |
| 2010 | 55801 | Thousand metric tons | 14.32% |
| 2011 | 58271 | Thousand metric tons | 4.43% |
| 2012 | 55531 | Thousand metric tons | -4.70% |
