Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 3230 | Thousand metric tons | NA |
| 2004 | 3269 | Thousand metric tons | 1.21% |
| 2005 | 3259 | Thousand metric tons | -0.31% |
| 2006 | 3265 | Thousand metric tons | 0.18% |
| 2007 | 3300 | Thousand metric tons | 1.07% |
