Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 15928 | Thousand metric tons | NA |
| 2004 | 16305 | Thousand metric tons | 2.37% |
| 2005 | 15327 | Thousand metric tons | -6.00% |
| 2006 | 15493 | Thousand metric tons | 1.08% |
| 2007 | 15569 | Thousand metric tons | 0.49% |
