Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 5707 | Thousand metric tons | NA |
| 2004 | 5949 | Thousand metric tons | 4.24% |
| 2005 | 5692 | Thousand metric tons | -4.32% |
| 2006 | 5435 | Thousand metric tons | -4.52% |
| 2007 | 5500 | Thousand metric tons | 1.20% |
