Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 364.305999755859 | Thousand metric tons | NA |
| 2004 | 365.835998535156 | Thousand metric tons | 0.42% |
| 2005 | 475.348999023438 | Thousand metric tons | 29.94% |
| 2006 | 771.226989746094 | Thousand metric tons | 62.24% |
| 2007 | 343.563995361328 | Thousand metric tons | -55.45% |
| 2008 | 350 | Thousand metric tons | 1.87% |
| 2009 | 330 | Thousand metric tons | -5.71% |
