Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 3844 | Thousand metric tons | NA |
| 2004 | 4023 | Thousand metric tons | 4.66% |
| 2005 | 4086 | Thousand metric tons | 1.57% |
| 2006 | 4099 | Thousand metric tons | 0.32% |
| 2007 | 3941 | Thousand metric tons | -3.85% |
