Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 19803 | Thousand metric tons | NA |
| 2004 | 20770 | Thousand metric tons | 4.88% |
| 2005 | 19481 | Thousand metric tons | -6.21% |
| 2006 | 19857 | Thousand metric tons | 1.93% |
| 2007 | 19252 | Thousand metric tons | -3.05% |
