Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2002 | 466 | Thousand metric tons | NA |
| 2003 | 506 | Thousand metric tons | 8.58 % |
| 2004 | 615 | Thousand metric tons | 21.54 % |
| 2005 | 726 | Thousand metric tons | 18.05 % |
| 2006 | 848.900024414063 | Thousand metric tons | 16.93 % |
| 2007 | 937.400024414063 | Thousand metric tons | 10.43 % |
| 2008 | 808 | Thousand metric tons | -13.80 % |
