Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 3944 | Thousand metric tons | NA |
| 2004 | 3902 | Thousand metric tons | -1.06% |
| 2005 | 4185 | Thousand metric tons | 7.25% |
| 2006 | 3974 | Thousand metric tons | -5.04% |
| 2007 | 4600 | Thousand metric tons | 15.75% |
