Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 6571 | Thousand metric tons | NA |
| 2004 | 6848 | Thousand metric tons | 4.22% |
| 2005 | 6919 | Thousand metric tons | 1.04% |
| 2006 | 6372 | Thousand metric tons | -7.91% |
| 2007 | 6400 | Thousand metric tons | 0.44% |
