Source: United States Geological Survey (USGS) Minerals Resources Program
Note: Check source table for details and footnotes
| Year | Production | Unit of Measure | % Change |
| 2003 | 16287 | Thousand metric tons | NA |
| 2004 | 17684 | Thousand metric tons | 8.58% |
| 2005 | 17711 | Thousand metric tons | 0.15% |
| 2006 | 18400 | Thousand metric tons | 3.89% |
| 2007 | 18400 | Thousand metric tons | 0.00% |
