Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 3000 | Thousand metric tons | NA |
| 2003 | 3100 | Thousand metric tons | 3.33% |
| 2004 | 3470 | Thousand metric tons | 11.94% |
| 2005 | 3690 | Thousand metric tons | 6.34% |
| 2006 | 4110 | Thousand metric tons | 11.38% |
| 2007 | 4420 | Thousand metric tons | 7.54% |
| 2008 | 5493 | Thousand metric tons | 24.28% |
| 2009 | 4990 | Thousand metric tons | -9.16% |
| 2010 | 5287 | Thousand metric tons | 5.95% |
| 2011 | 5706 | Thousand metric tons | 7.93% |
| 2012 | 5700 | Thousand metric tons | -0.11% |
