Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 9000 | Thousand metric tons | NA |
| 2003 | 9000 | Thousand metric tons | 0.00 % |
| 2004 | 11000 | Thousand metric tons | 22.22 % |
| 2005 | 12800 | Thousand metric tons | 16.36 % |
| 2006 | 14701.572265625 | Thousand metric tons | 14.86 % |
| 2007 | 15886 | Thousand metric tons | 8.06 % |
| 2008 | 17397.330078125 | Thousand metric tons | 9.51 % |
